mingw: fix isatty() after dup2()
[git] / graph.c
1 #include "cache.h"
2 #include "config.h"
3 #include "commit.h"
4 #include "color.h"
5 #include "graph.h"
6 #include "revision.h"
7 #include "argv-array.h"
8
9 /* Internal API */
10
11 /*
12  * Output a padding line in the graph.
13  * This is similar to graph_next_line().  However, it is guaranteed to
14  * never print the current commit line.  Instead, if the commit line is
15  * next, it will simply output a line of vertical padding, extending the
16  * branch lines downwards, but leaving them otherwise unchanged.
17  */
18 static void graph_padding_line(struct git_graph *graph, struct strbuf *sb);
19
20 /*
21  * Print a strbuf.  If the graph is non-NULL, all lines but the first will be
22  * prefixed with the graph output.
23  *
24  * If the strbuf ends with a newline, the output will end after this
25  * newline.  A new graph line will not be printed after the final newline.
26  * If the strbuf is empty, no output will be printed.
27  *
28  * Since the first line will not include the graph output, the caller is
29  * responsible for printing this line's graph (perhaps via
30  * graph_show_commit() or graph_show_oneline()) before calling
31  * graph_show_strbuf().
32  *
33  * Note that unlike some other graph display functions, you must pass the file
34  * handle directly. It is assumed that this is the same file handle as the
35  * file specified by the graph diff options. This is necessary so that
36  * graph_show_strbuf can be called even with a NULL graph.
37  */
38 static void graph_show_strbuf(struct git_graph *graph,
39                               FILE *file,
40                               struct strbuf const *sb);
41
42 /*
43  * TODO:
44  * - Limit the number of columns, similar to the way gitk does.
45  *   If we reach more than a specified number of columns, omit
46  *   sections of some columns.
47  */
48
49 struct column {
50         /*
51          * The parent commit of this column.
52          */
53         struct commit *commit;
54         /*
55          * The color to (optionally) print this column in.  This is an
56          * index into column_colors.
57          */
58         unsigned short color;
59 };
60
61 enum graph_state {
62         GRAPH_PADDING,
63         GRAPH_SKIP,
64         GRAPH_PRE_COMMIT,
65         GRAPH_COMMIT,
66         GRAPH_POST_MERGE,
67         GRAPH_COLLAPSING
68 };
69
70 static void graph_show_line_prefix(const struct diff_options *diffopt)
71 {
72         if (!diffopt || !diffopt->line_prefix)
73                 return;
74
75         fwrite(diffopt->line_prefix,
76                sizeof(char),
77                diffopt->line_prefix_length,
78                diffopt->file);
79 }
80
81 static const char **column_colors;
82 static unsigned short column_colors_max;
83
84 static void parse_graph_colors_config(struct argv_array *colors, const char *string)
85 {
86         const char *end, *start;
87
88         start = string;
89         end = string + strlen(string);
90         while (start < end) {
91                 const char *comma = strchrnul(start, ',');
92                 char color[COLOR_MAXLEN];
93
94                 if (!color_parse_mem(start, comma - start, color))
95                         argv_array_push(colors, color);
96                 else
97                         warning(_("ignore invalid color '%.*s' in log.graphColors"),
98                                 (int)(comma - start), start);
99                 start = comma + 1;
100         }
101         argv_array_push(colors, GIT_COLOR_RESET);
102 }
103
104 void graph_set_column_colors(const char **colors, unsigned short colors_max)
105 {
106         column_colors = colors;
107         column_colors_max = colors_max;
108 }
109
110 static const char *column_get_color_code(unsigned short color)
111 {
112         return column_colors[color];
113 }
114
115 static void strbuf_write_column(struct strbuf *sb, const struct column *c,
116                                 char col_char)
117 {
118         if (c->color < column_colors_max)
119                 strbuf_addstr(sb, column_get_color_code(c->color));
120         strbuf_addch(sb, col_char);
121         if (c->color < column_colors_max)
122                 strbuf_addstr(sb, column_get_color_code(column_colors_max));
123 }
124
125 struct git_graph {
126         /*
127          * The commit currently being processed
128          */
129         struct commit *commit;
130         /* The rev-info used for the current traversal */
131         struct rev_info *revs;
132         /*
133          * The number of interesting parents that this commit has.
134          *
135          * Note that this is not the same as the actual number of parents.
136          * This count excludes parents that won't be printed in the graph
137          * output, as determined by graph_is_interesting().
138          */
139         int num_parents;
140         /*
141          * The width of the graph output for this commit.
142          * All rows for this commit are padded to this width, so that
143          * messages printed after the graph output are aligned.
144          */
145         int width;
146         /*
147          * The next expansion row to print
148          * when state is GRAPH_PRE_COMMIT
149          */
150         int expansion_row;
151         /*
152          * The current output state.
153          * This tells us what kind of line graph_next_line() should output.
154          */
155         enum graph_state state;
156         /*
157          * The output state for the previous line of output.
158          * This is primarily used to determine how the first merge line
159          * should appear, based on the last line of the previous commit.
160          */
161         enum graph_state prev_state;
162         /*
163          * The index of the column that refers to this commit.
164          *
165          * If none of the incoming columns refer to this commit,
166          * this will be equal to num_columns.
167          */
168         int commit_index;
169         /*
170          * The commit_index for the previously displayed commit.
171          *
172          * This is used to determine how the first line of a merge
173          * graph output should appear, based on the last line of the
174          * previous commit.
175          */
176         int prev_commit_index;
177         /*
178          * The maximum number of columns that can be stored in the columns
179          * and new_columns arrays.  This is also half the number of entries
180          * that can be stored in the mapping and new_mapping arrays.
181          */
182         int column_capacity;
183         /*
184          * The number of columns (also called "branch lines" in some places)
185          */
186         int num_columns;
187         /*
188          * The number of columns in the new_columns array
189          */
190         int num_new_columns;
191         /*
192          * The number of entries in the mapping array
193          */
194         int mapping_size;
195         /*
196          * The column state before we output the current commit.
197          */
198         struct column *columns;
199         /*
200          * The new column state after we output the current commit.
201          * Only valid when state is GRAPH_COLLAPSING.
202          */
203         struct column *new_columns;
204         /*
205          * An array that tracks the current state of each
206          * character in the output line during state GRAPH_COLLAPSING.
207          * Each entry is -1 if this character is empty, or a non-negative
208          * integer if the character contains a branch line.  The value of
209          * the integer indicates the target position for this branch line.
210          * (I.e., this array maps the current column positions to their
211          * desired positions.)
212          *
213          * The maximum capacity of this array is always
214          * sizeof(int) * 2 * column_capacity.
215          */
216         int *mapping;
217         /*
218          * A temporary array for computing the next mapping state
219          * while we are outputting a mapping line.  This is stored as part
220          * of the git_graph simply so we don't have to allocate a new
221          * temporary array each time we have to output a collapsing line.
222          */
223         int *new_mapping;
224         /*
225          * The current default column color being used.  This is
226          * stored as an index into the array column_colors.
227          */
228         unsigned short default_column_color;
229 };
230
231 static struct strbuf *diff_output_prefix_callback(struct diff_options *opt, void *data)
232 {
233         struct git_graph *graph = data;
234         static struct strbuf msgbuf = STRBUF_INIT;
235
236         assert(opt);
237
238         strbuf_reset(&msgbuf);
239         if (opt->line_prefix)
240                 strbuf_add(&msgbuf, opt->line_prefix,
241                            opt->line_prefix_length);
242         if (graph)
243                 graph_padding_line(graph, &msgbuf);
244         return &msgbuf;
245 }
246
247 static const struct diff_options *default_diffopt;
248
249 void graph_setup_line_prefix(struct diff_options *diffopt)
250 {
251         default_diffopt = diffopt;
252
253         /* setup an output prefix callback if necessary */
254         if (diffopt && !diffopt->output_prefix)
255                 diffopt->output_prefix = diff_output_prefix_callback;
256 }
257
258
259 struct git_graph *graph_init(struct rev_info *opt)
260 {
261         struct git_graph *graph = xmalloc(sizeof(struct git_graph));
262
263         if (!column_colors) {
264                 char *string;
265                 if (git_config_get_string("log.graphcolors", &string)) {
266                         /* not configured -- use default */
267                         graph_set_column_colors(column_colors_ansi,
268                                                 column_colors_ansi_max);
269                 } else {
270                         static struct argv_array custom_colors = ARGV_ARRAY_INIT;
271                         argv_array_clear(&custom_colors);
272                         parse_graph_colors_config(&custom_colors, string);
273                         free(string);
274                         /* graph_set_column_colors takes a max-index, not a count */
275                         graph_set_column_colors(custom_colors.argv,
276                                                 custom_colors.argc - 1);
277                 }
278         }
279
280         graph->commit = NULL;
281         graph->revs = opt;
282         graph->num_parents = 0;
283         graph->expansion_row = 0;
284         graph->state = GRAPH_PADDING;
285         graph->prev_state = GRAPH_PADDING;
286         graph->commit_index = 0;
287         graph->prev_commit_index = 0;
288         graph->num_columns = 0;
289         graph->num_new_columns = 0;
290         graph->mapping_size = 0;
291         /*
292          * Start the column color at the maximum value, since we'll
293          * always increment it for the first commit we output.
294          * This way we start at 0 for the first commit.
295          */
296         graph->default_column_color = column_colors_max - 1;
297
298         /*
299          * Allocate a reasonably large default number of columns
300          * We'll automatically grow columns later if we need more room.
301          */
302         graph->column_capacity = 30;
303         ALLOC_ARRAY(graph->columns, graph->column_capacity);
304         ALLOC_ARRAY(graph->new_columns, graph->column_capacity);
305         ALLOC_ARRAY(graph->mapping, 2 * graph->column_capacity);
306         ALLOC_ARRAY(graph->new_mapping, 2 * graph->column_capacity);
307
308         /*
309          * The diff output prefix callback, with this we can make
310          * all the diff output to align with the graph lines.
311          */
312         opt->diffopt.output_prefix = diff_output_prefix_callback;
313         opt->diffopt.output_prefix_data = graph;
314
315         return graph;
316 }
317
318 static void graph_update_state(struct git_graph *graph, enum graph_state s)
319 {
320         graph->prev_state = graph->state;
321         graph->state = s;
322 }
323
324 static void graph_ensure_capacity(struct git_graph *graph, int num_columns)
325 {
326         if (graph->column_capacity >= num_columns)
327                 return;
328
329         do {
330                 graph->column_capacity *= 2;
331         } while (graph->column_capacity < num_columns);
332
333         REALLOC_ARRAY(graph->columns, graph->column_capacity);
334         REALLOC_ARRAY(graph->new_columns, graph->column_capacity);
335         REALLOC_ARRAY(graph->mapping, graph->column_capacity * 2);
336         REALLOC_ARRAY(graph->new_mapping, graph->column_capacity * 2);
337 }
338
339 /*
340  * Returns 1 if the commit will be printed in the graph output,
341  * and 0 otherwise.
342  */
343 static int graph_is_interesting(struct git_graph *graph, struct commit *commit)
344 {
345         /*
346          * If revs->boundary is set, commits whose children have
347          * been shown are always interesting, even if they have the
348          * UNINTERESTING or TREESAME flags set.
349          */
350         if (graph->revs && graph->revs->boundary) {
351                 if (commit->object.flags & CHILD_SHOWN)
352                         return 1;
353         }
354
355         /*
356          * Otherwise, use get_commit_action() to see if this commit is
357          * interesting
358          */
359         return get_commit_action(graph->revs, commit) == commit_show;
360 }
361
362 static struct commit_list *next_interesting_parent(struct git_graph *graph,
363                                                    struct commit_list *orig)
364 {
365         struct commit_list *list;
366
367         /*
368          * If revs->first_parent_only is set, only the first
369          * parent is interesting.  None of the others are.
370          */
371         if (graph->revs->first_parent_only)
372                 return NULL;
373
374         /*
375          * Return the next interesting commit after orig
376          */
377         for (list = orig->next; list; list = list->next) {
378                 if (graph_is_interesting(graph, list->item))
379                         return list;
380         }
381
382         return NULL;
383 }
384
385 static struct commit_list *first_interesting_parent(struct git_graph *graph)
386 {
387         struct commit_list *parents = graph->commit->parents;
388
389         /*
390          * If this commit has no parents, ignore it
391          */
392         if (!parents)
393                 return NULL;
394
395         /*
396          * If the first parent is interesting, return it
397          */
398         if (graph_is_interesting(graph, parents->item))
399                 return parents;
400
401         /*
402          * Otherwise, call next_interesting_parent() to get
403          * the next interesting parent
404          */
405         return next_interesting_parent(graph, parents);
406 }
407
408 static unsigned short graph_get_current_column_color(const struct git_graph *graph)
409 {
410         if (!want_color(graph->revs->diffopt.use_color))
411                 return column_colors_max;
412         return graph->default_column_color;
413 }
414
415 /*
416  * Update the graph's default column color.
417  */
418 static void graph_increment_column_color(struct git_graph *graph)
419 {
420         graph->default_column_color = (graph->default_column_color + 1) %
421                 column_colors_max;
422 }
423
424 static unsigned short graph_find_commit_color(const struct git_graph *graph,
425                                               const struct commit *commit)
426 {
427         int i;
428         for (i = 0; i < graph->num_columns; i++) {
429                 if (graph->columns[i].commit == commit)
430                         return graph->columns[i].color;
431         }
432         return graph_get_current_column_color(graph);
433 }
434
435 static void graph_insert_into_new_columns(struct git_graph *graph,
436                                           struct commit *commit,
437                                           int *mapping_index)
438 {
439         int i;
440
441         /*
442          * If the commit is already in the new_columns list, we don't need to
443          * add it.  Just update the mapping correctly.
444          */
445         for (i = 0; i < graph->num_new_columns; i++) {
446                 if (graph->new_columns[i].commit == commit) {
447                         graph->mapping[*mapping_index] = i;
448                         *mapping_index += 2;
449                         return;
450                 }
451         }
452
453         /*
454          * This commit isn't already in new_columns.  Add it.
455          */
456         graph->new_columns[graph->num_new_columns].commit = commit;
457         graph->new_columns[graph->num_new_columns].color = graph_find_commit_color(graph, commit);
458         graph->mapping[*mapping_index] = graph->num_new_columns;
459         *mapping_index += 2;
460         graph->num_new_columns++;
461 }
462
463 static void graph_update_width(struct git_graph *graph,
464                                int is_commit_in_existing_columns)
465 {
466         /*
467          * Compute the width needed to display the graph for this commit.
468          * This is the maximum width needed for any row.  All other rows
469          * will be padded to this width.
470          *
471          * Compute the number of columns in the widest row:
472          * Count each existing column (graph->num_columns), and each new
473          * column added by this commit.
474          */
475         int max_cols = graph->num_columns + graph->num_parents;
476
477         /*
478          * Even if the current commit has no parents to be printed, it
479          * still takes up a column for itself.
480          */
481         if (graph->num_parents < 1)
482                 max_cols++;
483
484         /*
485          * We added a column for the current commit as part of
486          * graph->num_parents.  If the current commit was already in
487          * graph->columns, then we have double counted it.
488          */
489         if (is_commit_in_existing_columns)
490                 max_cols--;
491
492         /*
493          * Each column takes up 2 spaces
494          */
495         graph->width = max_cols * 2;
496 }
497
498 static void graph_update_columns(struct git_graph *graph)
499 {
500         struct commit_list *parent;
501         int max_new_columns;
502         int mapping_idx;
503         int i, seen_this, is_commit_in_columns;
504
505         /*
506          * Swap graph->columns with graph->new_columns
507          * graph->columns contains the state for the previous commit,
508          * and new_columns now contains the state for our commit.
509          *
510          * We'll re-use the old columns array as storage to compute the new
511          * columns list for the commit after this one.
512          */
513         SWAP(graph->columns, graph->new_columns);
514         graph->num_columns = graph->num_new_columns;
515         graph->num_new_columns = 0;
516
517         /*
518          * Now update new_columns and mapping with the information for the
519          * commit after this one.
520          *
521          * First, make sure we have enough room.  At most, there will
522          * be graph->num_columns + graph->num_parents columns for the next
523          * commit.
524          */
525         max_new_columns = graph->num_columns + graph->num_parents;
526         graph_ensure_capacity(graph, max_new_columns);
527
528         /*
529          * Clear out graph->mapping
530          */
531         graph->mapping_size = 2 * max_new_columns;
532         for (i = 0; i < graph->mapping_size; i++)
533                 graph->mapping[i] = -1;
534
535         /*
536          * Populate graph->new_columns and graph->mapping
537          *
538          * Some of the parents of this commit may already be in
539          * graph->columns.  If so, graph->new_columns should only contain a
540          * single entry for each such commit.  graph->mapping should
541          * contain information about where each current branch line is
542          * supposed to end up after the collapsing is performed.
543          */
544         seen_this = 0;
545         mapping_idx = 0;
546         is_commit_in_columns = 1;
547         for (i = 0; i <= graph->num_columns; i++) {
548                 struct commit *col_commit;
549                 if (i == graph->num_columns) {
550                         if (seen_this)
551                                 break;
552                         is_commit_in_columns = 0;
553                         col_commit = graph->commit;
554                 } else {
555                         col_commit = graph->columns[i].commit;
556                 }
557
558                 if (col_commit == graph->commit) {
559                         int old_mapping_idx = mapping_idx;
560                         seen_this = 1;
561                         graph->commit_index = i;
562                         for (parent = first_interesting_parent(graph);
563                              parent;
564                              parent = next_interesting_parent(graph, parent)) {
565                                 /*
566                                  * If this is a merge, or the start of a new
567                                  * childless column, increment the current
568                                  * color.
569                                  */
570                                 if (graph->num_parents > 1 ||
571                                     !is_commit_in_columns) {
572                                         graph_increment_column_color(graph);
573                                 }
574                                 graph_insert_into_new_columns(graph,
575                                                               parent->item,
576                                                               &mapping_idx);
577                         }
578                         /*
579                          * We always need to increment mapping_idx by at
580                          * least 2, even if it has no interesting parents.
581                          * The current commit always takes up at least 2
582                          * spaces.
583                          */
584                         if (mapping_idx == old_mapping_idx)
585                                 mapping_idx += 2;
586                 } else {
587                         graph_insert_into_new_columns(graph, col_commit,
588                                                       &mapping_idx);
589                 }
590         }
591
592         /*
593          * Shrink mapping_size to be the minimum necessary
594          */
595         while (graph->mapping_size > 1 &&
596                graph->mapping[graph->mapping_size - 1] < 0)
597                 graph->mapping_size--;
598
599         /*
600          * Compute graph->width for this commit
601          */
602         graph_update_width(graph, is_commit_in_columns);
603 }
604
605 void graph_update(struct git_graph *graph, struct commit *commit)
606 {
607         struct commit_list *parent;
608
609         /*
610          * Set the new commit
611          */
612         graph->commit = commit;
613
614         /*
615          * Count how many interesting parents this commit has
616          */
617         graph->num_parents = 0;
618         for (parent = first_interesting_parent(graph);
619              parent;
620              parent = next_interesting_parent(graph, parent))
621         {
622                 graph->num_parents++;
623         }
624
625         /*
626          * Store the old commit_index in prev_commit_index.
627          * graph_update_columns() will update graph->commit_index for this
628          * commit.
629          */
630         graph->prev_commit_index = graph->commit_index;
631
632         /*
633          * Call graph_update_columns() to update
634          * columns, new_columns, and mapping.
635          */
636         graph_update_columns(graph);
637
638         graph->expansion_row = 0;
639
640         /*
641          * Update graph->state.
642          * Note that we don't call graph_update_state() here, since
643          * we don't want to update graph->prev_state.  No line for
644          * graph->state was ever printed.
645          *
646          * If the previous commit didn't get to the GRAPH_PADDING state,
647          * it never finished its output.  Goto GRAPH_SKIP, to print out
648          * a line to indicate that portion of the graph is missing.
649          *
650          * If there are 3 or more parents, we may need to print extra rows
651          * before the commit, to expand the branch lines around it and make
652          * room for it.  We need to do this only if there is a branch row
653          * (or more) to the right of this commit.
654          *
655          * If there are less than 3 parents, we can immediately print the
656          * commit line.
657          */
658         if (graph->state != GRAPH_PADDING)
659                 graph->state = GRAPH_SKIP;
660         else if (graph->num_parents >= 3 &&
661                  graph->commit_index < (graph->num_columns - 1))
662                 graph->state = GRAPH_PRE_COMMIT;
663         else
664                 graph->state = GRAPH_COMMIT;
665 }
666
667 static int graph_is_mapping_correct(struct git_graph *graph)
668 {
669         int i;
670
671         /*
672          * The mapping is up to date if each entry is at its target,
673          * or is 1 greater than its target.
674          * (If it is 1 greater than the target, '/' will be printed, so it
675          * will look correct on the next row.)
676          */
677         for (i = 0; i < graph->mapping_size; i++) {
678                 int target = graph->mapping[i];
679                 if (target < 0)
680                         continue;
681                 if (target == (i / 2))
682                         continue;
683                 return 0;
684         }
685
686         return 1;
687 }
688
689 static void graph_pad_horizontally(struct git_graph *graph, struct strbuf *sb,
690                                    int chars_written)
691 {
692         /*
693          * Add additional spaces to the end of the strbuf, so that all
694          * lines for a particular commit have the same width.
695          *
696          * This way, fields printed to the right of the graph will remain
697          * aligned for the entire commit.
698          */
699         if (chars_written < graph->width)
700                 strbuf_addchars(sb, ' ', graph->width - chars_written);
701 }
702
703 static void graph_output_padding_line(struct git_graph *graph,
704                                       struct strbuf *sb)
705 {
706         int i;
707
708         /*
709          * We could conceivable be called with a NULL commit
710          * if our caller has a bug, and invokes graph_next_line()
711          * immediately after graph_init(), without first calling
712          * graph_update().  Return without outputting anything in this
713          * case.
714          */
715         if (!graph->commit)
716                 return;
717
718         /*
719          * Output a padding row, that leaves all branch lines unchanged
720          */
721         for (i = 0; i < graph->num_new_columns; i++) {
722                 strbuf_write_column(sb, &graph->new_columns[i], '|');
723                 strbuf_addch(sb, ' ');
724         }
725
726         graph_pad_horizontally(graph, sb, graph->num_new_columns * 2);
727 }
728
729
730 int graph_width(struct git_graph *graph)
731 {
732         return graph->width;
733 }
734
735
736 static void graph_output_skip_line(struct git_graph *graph, struct strbuf *sb)
737 {
738         /*
739          * Output an ellipsis to indicate that a portion
740          * of the graph is missing.
741          */
742         strbuf_addstr(sb, "...");
743         graph_pad_horizontally(graph, sb, 3);
744
745         if (graph->num_parents >= 3 &&
746             graph->commit_index < (graph->num_columns - 1))
747                 graph_update_state(graph, GRAPH_PRE_COMMIT);
748         else
749                 graph_update_state(graph, GRAPH_COMMIT);
750 }
751
752 static void graph_output_pre_commit_line(struct git_graph *graph,
753                                          struct strbuf *sb)
754 {
755         int num_expansion_rows;
756         int i, seen_this;
757         int chars_written;
758
759         /*
760          * This function formats a row that increases the space around a commit
761          * with multiple parents, to make room for it.  It should only be
762          * called when there are 3 or more parents.
763          *
764          * We need 2 extra rows for every parent over 2.
765          */
766         assert(graph->num_parents >= 3);
767         num_expansion_rows = (graph->num_parents - 2) * 2;
768
769         /*
770          * graph->expansion_row tracks the current expansion row we are on.
771          * It should be in the range [0, num_expansion_rows - 1]
772          */
773         assert(0 <= graph->expansion_row &&
774                graph->expansion_row < num_expansion_rows);
775
776         /*
777          * Output the row
778          */
779         seen_this = 0;
780         chars_written = 0;
781         for (i = 0; i < graph->num_columns; i++) {
782                 struct column *col = &graph->columns[i];
783                 if (col->commit == graph->commit) {
784                         seen_this = 1;
785                         strbuf_write_column(sb, col, '|');
786                         strbuf_addchars(sb, ' ', graph->expansion_row);
787                         chars_written += 1 + graph->expansion_row;
788                 } else if (seen_this && (graph->expansion_row == 0)) {
789                         /*
790                          * This is the first line of the pre-commit output.
791                          * If the previous commit was a merge commit and
792                          * ended in the GRAPH_POST_MERGE state, all branch
793                          * lines after graph->prev_commit_index were
794                          * printed as "\" on the previous line.  Continue
795                          * to print them as "\" on this line.  Otherwise,
796                          * print the branch lines as "|".
797                          */
798                         if (graph->prev_state == GRAPH_POST_MERGE &&
799                             graph->prev_commit_index < i)
800                                 strbuf_write_column(sb, col, '\\');
801                         else
802                                 strbuf_write_column(sb, col, '|');
803                         chars_written++;
804                 } else if (seen_this && (graph->expansion_row > 0)) {
805                         strbuf_write_column(sb, col, '\\');
806                         chars_written++;
807                 } else {
808                         strbuf_write_column(sb, col, '|');
809                         chars_written++;
810                 }
811                 strbuf_addch(sb, ' ');
812                 chars_written++;
813         }
814
815         graph_pad_horizontally(graph, sb, chars_written);
816
817         /*
818          * Increment graph->expansion_row,
819          * and move to state GRAPH_COMMIT if necessary
820          */
821         graph->expansion_row++;
822         if (graph->expansion_row >= num_expansion_rows)
823                 graph_update_state(graph, GRAPH_COMMIT);
824 }
825
826 static void graph_output_commit_char(struct git_graph *graph, struct strbuf *sb)
827 {
828         /*
829          * For boundary commits, print 'o'
830          * (We should only see boundary commits when revs->boundary is set.)
831          */
832         if (graph->commit->object.flags & BOUNDARY) {
833                 assert(graph->revs->boundary);
834                 strbuf_addch(sb, 'o');
835                 return;
836         }
837
838         /*
839          * get_revision_mark() handles all other cases without assert()
840          */
841         strbuf_addstr(sb, get_revision_mark(graph->revs, graph->commit));
842 }
843
844 /*
845  * Draw the horizontal dashes of an octopus merge and return the number of
846  * characters written.
847  */
848 static int graph_draw_octopus_merge(struct git_graph *graph,
849                                     struct strbuf *sb)
850 {
851         /*
852          * Here dashless_parents represents the number of parents which don't
853          * need to have dashes (the edges labeled "0" and "1").  And
854          * dashful_parents are the remaining ones.
855          *
856          * | *---.
857          * | |\ \ \
858          * | | | | |
859          * x 0 1 2 3
860          *
861          */
862         const int dashless_parents = 2;
863         int dashful_parents = graph->num_parents - dashless_parents;
864
865         /*
866          * Usually, we add one new column for each parent (like the diagram
867          * above) but sometimes the first parent goes into an existing column,
868          * like this:
869          *
870          * | *---.
871          * | |\ \ \
872          * |/ / / /
873          * x 0 1 2
874          *
875          * In which case the number of parents will be one greater than the
876          * number of added columns.
877          */
878         int added_cols = (graph->num_new_columns - graph->num_columns);
879         int parent_in_old_cols = graph->num_parents - added_cols;
880
881         /*
882          * In both cases, commit_index corresponds to the edge labeled "0".
883          */
884         int first_col = graph->commit_index + dashless_parents
885             - parent_in_old_cols;
886
887         int i;
888         for (i = 0; i < dashful_parents; i++) {
889                 strbuf_write_column(sb, &graph->new_columns[i+first_col], '-');
890                 strbuf_write_column(sb, &graph->new_columns[i+first_col],
891                                     i == dashful_parents-1 ? '.' : '-');
892         }
893         return 2 * dashful_parents;
894 }
895
896 static void graph_output_commit_line(struct git_graph *graph, struct strbuf *sb)
897 {
898         int seen_this = 0;
899         int i, chars_written;
900
901         /*
902          * Output the row containing this commit
903          * Iterate up to and including graph->num_columns,
904          * since the current commit may not be in any of the existing
905          * columns.  (This happens when the current commit doesn't have any
906          * children that we have already processed.)
907          */
908         seen_this = 0;
909         chars_written = 0;
910         for (i = 0; i <= graph->num_columns; i++) {
911                 struct column *col = &graph->columns[i];
912                 struct commit *col_commit;
913                 if (i == graph->num_columns) {
914                         if (seen_this)
915                                 break;
916                         col_commit = graph->commit;
917                 } else {
918                         col_commit = graph->columns[i].commit;
919                 }
920
921                 if (col_commit == graph->commit) {
922                         seen_this = 1;
923                         graph_output_commit_char(graph, sb);
924                         chars_written++;
925
926                         if (graph->num_parents > 2)
927                                 chars_written += graph_draw_octopus_merge(graph,
928                                                                           sb);
929                 } else if (seen_this && (graph->num_parents > 2)) {
930                         strbuf_write_column(sb, col, '\\');
931                         chars_written++;
932                 } else if (seen_this && (graph->num_parents == 2)) {
933                         /*
934                          * This is a 2-way merge commit.
935                          * There is no GRAPH_PRE_COMMIT stage for 2-way
936                          * merges, so this is the first line of output
937                          * for this commit.  Check to see what the previous
938                          * line of output was.
939                          *
940                          * If it was GRAPH_POST_MERGE, the branch line
941                          * coming into this commit may have been '\',
942                          * and not '|' or '/'.  If so, output the branch
943                          * line as '\' on this line, instead of '|'.  This
944                          * makes the output look nicer.
945                          */
946                         if (graph->prev_state == GRAPH_POST_MERGE &&
947                             graph->prev_commit_index < i)
948                                 strbuf_write_column(sb, col, '\\');
949                         else
950                                 strbuf_write_column(sb, col, '|');
951                         chars_written++;
952                 } else {
953                         strbuf_write_column(sb, col, '|');
954                         chars_written++;
955                 }
956                 strbuf_addch(sb, ' ');
957                 chars_written++;
958         }
959
960         graph_pad_horizontally(graph, sb, chars_written);
961
962         /*
963          * Update graph->state
964          */
965         if (graph->num_parents > 1)
966                 graph_update_state(graph, GRAPH_POST_MERGE);
967         else if (graph_is_mapping_correct(graph))
968                 graph_update_state(graph, GRAPH_PADDING);
969         else
970                 graph_update_state(graph, GRAPH_COLLAPSING);
971 }
972
973 static struct column *find_new_column_by_commit(struct git_graph *graph,
974                                                 struct commit *commit)
975 {
976         int i;
977         for (i = 0; i < graph->num_new_columns; i++) {
978                 if (graph->new_columns[i].commit == commit)
979                         return &graph->new_columns[i];
980         }
981         return NULL;
982 }
983
984 static void graph_output_post_merge_line(struct git_graph *graph, struct strbuf *sb)
985 {
986         int seen_this = 0;
987         int i, j, chars_written;
988
989         /*
990          * Output the post-merge row
991          */
992         chars_written = 0;
993         for (i = 0; i <= graph->num_columns; i++) {
994                 struct column *col = &graph->columns[i];
995                 struct commit *col_commit;
996                 if (i == graph->num_columns) {
997                         if (seen_this)
998                                 break;
999                         col_commit = graph->commit;
1000                 } else {
1001                         col_commit = col->commit;
1002                 }
1003
1004                 if (col_commit == graph->commit) {
1005                         /*
1006                          * Since the current commit is a merge find
1007                          * the columns for the parent commits in
1008                          * new_columns and use those to format the
1009                          * edges.
1010                          */
1011                         struct commit_list *parents = NULL;
1012                         struct column *par_column;
1013                         seen_this = 1;
1014                         parents = first_interesting_parent(graph);
1015                         assert(parents);
1016                         par_column = find_new_column_by_commit(graph, parents->item);
1017                         assert(par_column);
1018
1019                         strbuf_write_column(sb, par_column, '|');
1020                         chars_written++;
1021                         for (j = 0; j < graph->num_parents - 1; j++) {
1022                                 parents = next_interesting_parent(graph, parents);
1023                                 assert(parents);
1024                                 par_column = find_new_column_by_commit(graph, parents->item);
1025                                 assert(par_column);
1026                                 strbuf_write_column(sb, par_column, '\\');
1027                                 strbuf_addch(sb, ' ');
1028                         }
1029                         chars_written += j * 2;
1030                 } else if (seen_this) {
1031                         strbuf_write_column(sb, col, '\\');
1032                         strbuf_addch(sb, ' ');
1033                         chars_written += 2;
1034                 } else {
1035                         strbuf_write_column(sb, col, '|');
1036                         strbuf_addch(sb, ' ');
1037                         chars_written += 2;
1038                 }
1039         }
1040
1041         graph_pad_horizontally(graph, sb, chars_written);
1042
1043         /*
1044          * Update graph->state
1045          */
1046         if (graph_is_mapping_correct(graph))
1047                 graph_update_state(graph, GRAPH_PADDING);
1048         else
1049                 graph_update_state(graph, GRAPH_COLLAPSING);
1050 }
1051
1052 static void graph_output_collapsing_line(struct git_graph *graph, struct strbuf *sb)
1053 {
1054         int i;
1055         short used_horizontal = 0;
1056         int horizontal_edge = -1;
1057         int horizontal_edge_target = -1;
1058
1059         /*
1060          * Clear out the new_mapping array
1061          */
1062         for (i = 0; i < graph->mapping_size; i++)
1063                 graph->new_mapping[i] = -1;
1064
1065         for (i = 0; i < graph->mapping_size; i++) {
1066                 int target = graph->mapping[i];
1067                 if (target < 0)
1068                         continue;
1069
1070                 /*
1071                  * Since update_columns() always inserts the leftmost
1072                  * column first, each branch's target location should
1073                  * always be either its current location or to the left of
1074                  * its current location.
1075                  *
1076                  * We never have to move branches to the right.  This makes
1077                  * the graph much more legible, since whenever branches
1078                  * cross, only one is moving directions.
1079                  */
1080                 assert(target * 2 <= i);
1081
1082                 if (target * 2 == i) {
1083                         /*
1084                          * This column is already in the
1085                          * correct place
1086                          */
1087                         assert(graph->new_mapping[i] == -1);
1088                         graph->new_mapping[i] = target;
1089                 } else if (graph->new_mapping[i - 1] < 0) {
1090                         /*
1091                          * Nothing is to the left.
1092                          * Move to the left by one
1093                          */
1094                         graph->new_mapping[i - 1] = target;
1095                         /*
1096                          * If there isn't already an edge moving horizontally
1097                          * select this one.
1098                          */
1099                         if (horizontal_edge == -1) {
1100                                 int j;
1101                                 horizontal_edge = i;
1102                                 horizontal_edge_target = target;
1103                                 /*
1104                                  * The variable target is the index of the graph
1105                                  * column, and therefore target*2+3 is the
1106                                  * actual screen column of the first horizontal
1107                                  * line.
1108                                  */
1109                                 for (j = (target * 2)+3; j < (i - 2); j += 2)
1110                                         graph->new_mapping[j] = target;
1111                         }
1112                 } else if (graph->new_mapping[i - 1] == target) {
1113                         /*
1114                          * There is a branch line to our left
1115                          * already, and it is our target.  We
1116                          * combine with this line, since we share
1117                          * the same parent commit.
1118                          *
1119                          * We don't have to add anything to the
1120                          * output or new_mapping, since the
1121                          * existing branch line has already taken
1122                          * care of it.
1123                          */
1124                 } else {
1125                         /*
1126                          * There is a branch line to our left,
1127                          * but it isn't our target.  We need to
1128                          * cross over it.
1129                          *
1130                          * The space just to the left of this
1131                          * branch should always be empty.
1132                          *
1133                          * The branch to the left of that space
1134                          * should be our eventual target.
1135                          */
1136                         assert(graph->new_mapping[i - 1] > target);
1137                         assert(graph->new_mapping[i - 2] < 0);
1138                         assert(graph->new_mapping[i - 3] == target);
1139                         graph->new_mapping[i - 2] = target;
1140                         /*
1141                          * Mark this branch as the horizontal edge to
1142                          * prevent any other edges from moving
1143                          * horizontally.
1144                          */
1145                         if (horizontal_edge == -1)
1146                                 horizontal_edge = i;
1147                 }
1148         }
1149
1150         /*
1151          * The new mapping may be 1 smaller than the old mapping
1152          */
1153         if (graph->new_mapping[graph->mapping_size - 1] < 0)
1154                 graph->mapping_size--;
1155
1156         /*
1157          * Output out a line based on the new mapping info
1158          */
1159         for (i = 0; i < graph->mapping_size; i++) {
1160                 int target = graph->new_mapping[i];
1161                 if (target < 0)
1162                         strbuf_addch(sb, ' ');
1163                 else if (target * 2 == i)
1164                         strbuf_write_column(sb, &graph->new_columns[target], '|');
1165                 else if (target == horizontal_edge_target &&
1166                          i != horizontal_edge - 1) {
1167                                 /*
1168                                  * Set the mappings for all but the
1169                                  * first segment to -1 so that they
1170                                  * won't continue into the next line.
1171                                  */
1172                                 if (i != (target * 2)+3)
1173                                         graph->new_mapping[i] = -1;
1174                                 used_horizontal = 1;
1175                         strbuf_write_column(sb, &graph->new_columns[target], '_');
1176                 } else {
1177                         if (used_horizontal && i < horizontal_edge)
1178                                 graph->new_mapping[i] = -1;
1179                         strbuf_write_column(sb, &graph->new_columns[target], '/');
1180
1181                 }
1182         }
1183
1184         graph_pad_horizontally(graph, sb, graph->mapping_size);
1185
1186         /*
1187          * Swap mapping and new_mapping
1188          */
1189         SWAP(graph->mapping, graph->new_mapping);
1190
1191         /*
1192          * If graph->mapping indicates that all of the branch lines
1193          * are already in the correct positions, we are done.
1194          * Otherwise, we need to collapse some branch lines together.
1195          */
1196         if (graph_is_mapping_correct(graph))
1197                 graph_update_state(graph, GRAPH_PADDING);
1198 }
1199
1200 int graph_next_line(struct git_graph *graph, struct strbuf *sb)
1201 {
1202         switch (graph->state) {
1203         case GRAPH_PADDING:
1204                 graph_output_padding_line(graph, sb);
1205                 return 0;
1206         case GRAPH_SKIP:
1207                 graph_output_skip_line(graph, sb);
1208                 return 0;
1209         case GRAPH_PRE_COMMIT:
1210                 graph_output_pre_commit_line(graph, sb);
1211                 return 0;
1212         case GRAPH_COMMIT:
1213                 graph_output_commit_line(graph, sb);
1214                 return 1;
1215         case GRAPH_POST_MERGE:
1216                 graph_output_post_merge_line(graph, sb);
1217                 return 0;
1218         case GRAPH_COLLAPSING:
1219                 graph_output_collapsing_line(graph, sb);
1220                 return 0;
1221         }
1222
1223         assert(0);
1224         return 0;
1225 }
1226
1227 static void graph_padding_line(struct git_graph *graph, struct strbuf *sb)
1228 {
1229         int i;
1230         int chars_written = 0;
1231
1232         if (graph->state != GRAPH_COMMIT) {
1233                 graph_next_line(graph, sb);
1234                 return;
1235         }
1236
1237         /*
1238          * Output the row containing this commit
1239          * Iterate up to and including graph->num_columns,
1240          * since the current commit may not be in any of the existing
1241          * columns.  (This happens when the current commit doesn't have any
1242          * children that we have already processed.)
1243          */
1244         for (i = 0; i < graph->num_columns; i++) {
1245                 struct column *col = &graph->columns[i];
1246
1247                 strbuf_write_column(sb, col, '|');
1248                 chars_written++;
1249
1250                 if (col->commit == graph->commit && graph->num_parents > 2) {
1251                         int len = (graph->num_parents - 2) * 2;
1252                         strbuf_addchars(sb, ' ', len);
1253                         chars_written += len;
1254                 } else {
1255                         strbuf_addch(sb, ' ');
1256                         chars_written++;
1257                 }
1258         }
1259
1260         graph_pad_horizontally(graph, sb, chars_written);
1261
1262         /*
1263          * Update graph->prev_state since we have output a padding line
1264          */
1265         graph->prev_state = GRAPH_PADDING;
1266 }
1267
1268 int graph_is_commit_finished(struct git_graph const *graph)
1269 {
1270         return (graph->state == GRAPH_PADDING);
1271 }
1272
1273 void graph_show_commit(struct git_graph *graph)
1274 {
1275         struct strbuf msgbuf = STRBUF_INIT;
1276         int shown_commit_line = 0;
1277
1278         graph_show_line_prefix(default_diffopt);
1279
1280         if (!graph)
1281                 return;
1282
1283         /*
1284          * When showing a diff of a merge against each of its parents, we
1285          * are called once for each parent without graph_update having been
1286          * called.  In this case, simply output a single padding line.
1287          */
1288         if (graph_is_commit_finished(graph)) {
1289                 graph_show_padding(graph);
1290                 shown_commit_line = 1;
1291         }
1292
1293         while (!shown_commit_line && !graph_is_commit_finished(graph)) {
1294                 shown_commit_line = graph_next_line(graph, &msgbuf);
1295                 fwrite(msgbuf.buf, sizeof(char), msgbuf.len,
1296                         graph->revs->diffopt.file);
1297                 if (!shown_commit_line) {
1298                         putc('\n', graph->revs->diffopt.file);
1299                         graph_show_line_prefix(&graph->revs->diffopt);
1300                 }
1301                 strbuf_setlen(&msgbuf, 0);
1302         }
1303
1304         strbuf_release(&msgbuf);
1305 }
1306
1307 void graph_show_oneline(struct git_graph *graph)
1308 {
1309         struct strbuf msgbuf = STRBUF_INIT;
1310
1311         graph_show_line_prefix(default_diffopt);
1312
1313         if (!graph)
1314                 return;
1315
1316         graph_next_line(graph, &msgbuf);
1317         fwrite(msgbuf.buf, sizeof(char), msgbuf.len, graph->revs->diffopt.file);
1318         strbuf_release(&msgbuf);
1319 }
1320
1321 void graph_show_padding(struct git_graph *graph)
1322 {
1323         struct strbuf msgbuf = STRBUF_INIT;
1324
1325         graph_show_line_prefix(default_diffopt);
1326
1327         if (!graph)
1328                 return;
1329
1330         graph_padding_line(graph, &msgbuf);
1331         fwrite(msgbuf.buf, sizeof(char), msgbuf.len, graph->revs->diffopt.file);
1332         strbuf_release(&msgbuf);
1333 }
1334
1335 int graph_show_remainder(struct git_graph *graph)
1336 {
1337         struct strbuf msgbuf = STRBUF_INIT;
1338         int shown = 0;
1339
1340         graph_show_line_prefix(default_diffopt);
1341
1342         if (!graph)
1343                 return 0;
1344
1345         if (graph_is_commit_finished(graph))
1346                 return 0;
1347
1348         for (;;) {
1349                 graph_next_line(graph, &msgbuf);
1350                 fwrite(msgbuf.buf, sizeof(char), msgbuf.len,
1351                         graph->revs->diffopt.file);
1352                 strbuf_setlen(&msgbuf, 0);
1353                 shown = 1;
1354
1355                 if (!graph_is_commit_finished(graph)) {
1356                         putc('\n', graph->revs->diffopt.file);
1357                         graph_show_line_prefix(&graph->revs->diffopt);
1358                 } else {
1359                         break;
1360                 }
1361         }
1362         strbuf_release(&msgbuf);
1363
1364         return shown;
1365 }
1366
1367 static void graph_show_strbuf(struct git_graph *graph,
1368                               FILE *file,
1369                               struct strbuf const *sb)
1370 {
1371         char *p;
1372
1373         /*
1374          * Print the strbuf line by line,
1375          * and display the graph info before each line but the first.
1376          */
1377         p = sb->buf;
1378         while (p) {
1379                 size_t len;
1380                 char *next_p = strchr(p, '\n');
1381                 if (next_p) {
1382                         next_p++;
1383                         len = next_p - p;
1384                 } else {
1385                         len = (sb->buf + sb->len) - p;
1386                 }
1387                 fwrite(p, sizeof(char), len, file);
1388                 if (next_p && *next_p != '\0')
1389                         graph_show_oneline(graph);
1390                 p = next_p;
1391         }
1392 }
1393
1394 void graph_show_commit_msg(struct git_graph *graph,
1395                            FILE *file,
1396                            struct strbuf const *sb)
1397 {
1398         int newline_terminated;
1399
1400         /*
1401          * Show the commit message
1402          */
1403         graph_show_strbuf(graph, file, sb);
1404
1405         if (!graph)
1406                 return;
1407
1408         newline_terminated = (sb->len && sb->buf[sb->len - 1] == '\n');
1409
1410         /*
1411          * If there is more output needed for this commit, show it now
1412          */
1413         if (!graph_is_commit_finished(graph)) {
1414                 /*
1415                  * If sb doesn't have a terminating newline, print one now,
1416                  * so we can start the remainder of the graph output on a
1417                  * new line.
1418                  */
1419                 if (!newline_terminated)
1420                         putc('\n', file);
1421
1422                 graph_show_remainder(graph);
1423
1424                 /*
1425                  * If sb ends with a newline, our output should too.
1426                  */
1427                 if (newline_terminated)
1428                         putc('\n', file);
1429         }
1430 }