diff-highlight: add clean target to Makefile
[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         int extra;
700         if (chars_written >= graph->width)
701                 return;
702
703         extra = graph->width - chars_written;
704         strbuf_addf(sb, "%*s", (int) extra, "");
705 }
706
707 static void graph_output_padding_line(struct git_graph *graph,
708                                       struct strbuf *sb)
709 {
710         int i;
711
712         /*
713          * We could conceivable be called with a NULL commit
714          * if our caller has a bug, and invokes graph_next_line()
715          * immediately after graph_init(), without first calling
716          * graph_update().  Return without outputting anything in this
717          * case.
718          */
719         if (!graph->commit)
720                 return;
721
722         /*
723          * Output a padding row, that leaves all branch lines unchanged
724          */
725         for (i = 0; i < graph->num_new_columns; i++) {
726                 strbuf_write_column(sb, &graph->new_columns[i], '|');
727                 strbuf_addch(sb, ' ');
728         }
729
730         graph_pad_horizontally(graph, sb, graph->num_new_columns * 2);
731 }
732
733
734 int graph_width(struct git_graph *graph)
735 {
736         return graph->width;
737 }
738
739
740 static void graph_output_skip_line(struct git_graph *graph, struct strbuf *sb)
741 {
742         /*
743          * Output an ellipsis to indicate that a portion
744          * of the graph is missing.
745          */
746         strbuf_addstr(sb, "...");
747         graph_pad_horizontally(graph, sb, 3);
748
749         if (graph->num_parents >= 3 &&
750             graph->commit_index < (graph->num_columns - 1))
751                 graph_update_state(graph, GRAPH_PRE_COMMIT);
752         else
753                 graph_update_state(graph, GRAPH_COMMIT);
754 }
755
756 static void graph_output_pre_commit_line(struct git_graph *graph,
757                                          struct strbuf *sb)
758 {
759         int num_expansion_rows;
760         int i, seen_this;
761         int chars_written;
762
763         /*
764          * This function formats a row that increases the space around a commit
765          * with multiple parents, to make room for it.  It should only be
766          * called when there are 3 or more parents.
767          *
768          * We need 2 extra rows for every parent over 2.
769          */
770         assert(graph->num_parents >= 3);
771         num_expansion_rows = (graph->num_parents - 2) * 2;
772
773         /*
774          * graph->expansion_row tracks the current expansion row we are on.
775          * It should be in the range [0, num_expansion_rows - 1]
776          */
777         assert(0 <= graph->expansion_row &&
778                graph->expansion_row < num_expansion_rows);
779
780         /*
781          * Output the row
782          */
783         seen_this = 0;
784         chars_written = 0;
785         for (i = 0; i < graph->num_columns; i++) {
786                 struct column *col = &graph->columns[i];
787                 if (col->commit == graph->commit) {
788                         seen_this = 1;
789                         strbuf_write_column(sb, col, '|');
790                         strbuf_addf(sb, "%*s", graph->expansion_row, "");
791                         chars_written += 1 + graph->expansion_row;
792                 } else if (seen_this && (graph->expansion_row == 0)) {
793                         /*
794                          * This is the first line of the pre-commit output.
795                          * If the previous commit was a merge commit and
796                          * ended in the GRAPH_POST_MERGE state, all branch
797                          * lines after graph->prev_commit_index were
798                          * printed as "\" on the previous line.  Continue
799                          * to print them as "\" on this line.  Otherwise,
800                          * print the branch lines as "|".
801                          */
802                         if (graph->prev_state == GRAPH_POST_MERGE &&
803                             graph->prev_commit_index < i)
804                                 strbuf_write_column(sb, col, '\\');
805                         else
806                                 strbuf_write_column(sb, col, '|');
807                         chars_written++;
808                 } else if (seen_this && (graph->expansion_row > 0)) {
809                         strbuf_write_column(sb, col, '\\');
810                         chars_written++;
811                 } else {
812                         strbuf_write_column(sb, col, '|');
813                         chars_written++;
814                 }
815                 strbuf_addch(sb, ' ');
816                 chars_written++;
817         }
818
819         graph_pad_horizontally(graph, sb, chars_written);
820
821         /*
822          * Increment graph->expansion_row,
823          * and move to state GRAPH_COMMIT if necessary
824          */
825         graph->expansion_row++;
826         if (graph->expansion_row >= num_expansion_rows)
827                 graph_update_state(graph, GRAPH_COMMIT);
828 }
829
830 static void graph_output_commit_char(struct git_graph *graph, struct strbuf *sb)
831 {
832         /*
833          * For boundary commits, print 'o'
834          * (We should only see boundary commits when revs->boundary is set.)
835          */
836         if (graph->commit->object.flags & BOUNDARY) {
837                 assert(graph->revs->boundary);
838                 strbuf_addch(sb, 'o');
839                 return;
840         }
841
842         /*
843          * get_revision_mark() handles all other cases without assert()
844          */
845         strbuf_addstr(sb, get_revision_mark(graph->revs, graph->commit));
846 }
847
848 /*
849  * Draw an octopus merge and return the number of characters written.
850  */
851 static int graph_draw_octopus_merge(struct git_graph *graph,
852                                     struct strbuf *sb)
853 {
854         /*
855          * Here dashless_commits represents the number of parents
856          * which don't need to have dashes (because their edges fit
857          * neatly under the commit).
858          */
859         const int dashless_commits = 2;
860         int col_num, i;
861         int num_dashes =
862                 ((graph->num_parents - dashless_commits) * 2) - 1;
863         for (i = 0; i < num_dashes; i++) {
864                 col_num = (i / 2) + dashless_commits + graph->commit_index;
865                 strbuf_write_column(sb, &graph->new_columns[col_num], '-');
866         }
867         col_num = (i / 2) + dashless_commits + graph->commit_index;
868         strbuf_write_column(sb, &graph->new_columns[col_num], '.');
869         return num_dashes + 1;
870 }
871
872 static void graph_output_commit_line(struct git_graph *graph, struct strbuf *sb)
873 {
874         int seen_this = 0;
875         int i, chars_written;
876
877         /*
878          * Output the row containing this commit
879          * Iterate up to and including graph->num_columns,
880          * since the current commit may not be in any of the existing
881          * columns.  (This happens when the current commit doesn't have any
882          * children that we have already processed.)
883          */
884         seen_this = 0;
885         chars_written = 0;
886         for (i = 0; i <= graph->num_columns; i++) {
887                 struct column *col = &graph->columns[i];
888                 struct commit *col_commit;
889                 if (i == graph->num_columns) {
890                         if (seen_this)
891                                 break;
892                         col_commit = graph->commit;
893                 } else {
894                         col_commit = graph->columns[i].commit;
895                 }
896
897                 if (col_commit == graph->commit) {
898                         seen_this = 1;
899                         graph_output_commit_char(graph, sb);
900                         chars_written++;
901
902                         if (graph->num_parents > 2)
903                                 chars_written += graph_draw_octopus_merge(graph,
904                                                                           sb);
905                 } else if (seen_this && (graph->num_parents > 2)) {
906                         strbuf_write_column(sb, col, '\\');
907                         chars_written++;
908                 } else if (seen_this && (graph->num_parents == 2)) {
909                         /*
910                          * This is a 2-way merge commit.
911                          * There is no GRAPH_PRE_COMMIT stage for 2-way
912                          * merges, so this is the first line of output
913                          * for this commit.  Check to see what the previous
914                          * line of output was.
915                          *
916                          * If it was GRAPH_POST_MERGE, the branch line
917                          * coming into this commit may have been '\',
918                          * and not '|' or '/'.  If so, output the branch
919                          * line as '\' on this line, instead of '|'.  This
920                          * makes the output look nicer.
921                          */
922                         if (graph->prev_state == GRAPH_POST_MERGE &&
923                             graph->prev_commit_index < i)
924                                 strbuf_write_column(sb, col, '\\');
925                         else
926                                 strbuf_write_column(sb, col, '|');
927                         chars_written++;
928                 } else {
929                         strbuf_write_column(sb, col, '|');
930                         chars_written++;
931                 }
932                 strbuf_addch(sb, ' ');
933                 chars_written++;
934         }
935
936         graph_pad_horizontally(graph, sb, chars_written);
937
938         /*
939          * Update graph->state
940          */
941         if (graph->num_parents > 1)
942                 graph_update_state(graph, GRAPH_POST_MERGE);
943         else if (graph_is_mapping_correct(graph))
944                 graph_update_state(graph, GRAPH_PADDING);
945         else
946                 graph_update_state(graph, GRAPH_COLLAPSING);
947 }
948
949 static struct column *find_new_column_by_commit(struct git_graph *graph,
950                                                 struct commit *commit)
951 {
952         int i;
953         for (i = 0; i < graph->num_new_columns; i++) {
954                 if (graph->new_columns[i].commit == commit)
955                         return &graph->new_columns[i];
956         }
957         return NULL;
958 }
959
960 static void graph_output_post_merge_line(struct git_graph *graph, struct strbuf *sb)
961 {
962         int seen_this = 0;
963         int i, j, chars_written;
964
965         /*
966          * Output the post-merge row
967          */
968         chars_written = 0;
969         for (i = 0; i <= graph->num_columns; i++) {
970                 struct column *col = &graph->columns[i];
971                 struct commit *col_commit;
972                 if (i == graph->num_columns) {
973                         if (seen_this)
974                                 break;
975                         col_commit = graph->commit;
976                 } else {
977                         col_commit = col->commit;
978                 }
979
980                 if (col_commit == graph->commit) {
981                         /*
982                          * Since the current commit is a merge find
983                          * the columns for the parent commits in
984                          * new_columns and use those to format the
985                          * edges.
986                          */
987                         struct commit_list *parents = NULL;
988                         struct column *par_column;
989                         seen_this = 1;
990                         parents = first_interesting_parent(graph);
991                         assert(parents);
992                         par_column = find_new_column_by_commit(graph, parents->item);
993                         assert(par_column);
994
995                         strbuf_write_column(sb, par_column, '|');
996                         chars_written++;
997                         for (j = 0; j < graph->num_parents - 1; j++) {
998                                 parents = next_interesting_parent(graph, parents);
999                                 assert(parents);
1000                                 par_column = find_new_column_by_commit(graph, parents->item);
1001                                 assert(par_column);
1002                                 strbuf_write_column(sb, par_column, '\\');
1003                                 strbuf_addch(sb, ' ');
1004                         }
1005                         chars_written += j * 2;
1006                 } else if (seen_this) {
1007                         strbuf_write_column(sb, col, '\\');
1008                         strbuf_addch(sb, ' ');
1009                         chars_written += 2;
1010                 } else {
1011                         strbuf_write_column(sb, col, '|');
1012                         strbuf_addch(sb, ' ');
1013                         chars_written += 2;
1014                 }
1015         }
1016
1017         graph_pad_horizontally(graph, sb, chars_written);
1018
1019         /*
1020          * Update graph->state
1021          */
1022         if (graph_is_mapping_correct(graph))
1023                 graph_update_state(graph, GRAPH_PADDING);
1024         else
1025                 graph_update_state(graph, GRAPH_COLLAPSING);
1026 }
1027
1028 static void graph_output_collapsing_line(struct git_graph *graph, struct strbuf *sb)
1029 {
1030         int i;
1031         short used_horizontal = 0;
1032         int horizontal_edge = -1;
1033         int horizontal_edge_target = -1;
1034
1035         /*
1036          * Clear out the new_mapping array
1037          */
1038         for (i = 0; i < graph->mapping_size; i++)
1039                 graph->new_mapping[i] = -1;
1040
1041         for (i = 0; i < graph->mapping_size; i++) {
1042                 int target = graph->mapping[i];
1043                 if (target < 0)
1044                         continue;
1045
1046                 /*
1047                  * Since update_columns() always inserts the leftmost
1048                  * column first, each branch's target location should
1049                  * always be either its current location or to the left of
1050                  * its current location.
1051                  *
1052                  * We never have to move branches to the right.  This makes
1053                  * the graph much more legible, since whenever branches
1054                  * cross, only one is moving directions.
1055                  */
1056                 assert(target * 2 <= i);
1057
1058                 if (target * 2 == i) {
1059                         /*
1060                          * This column is already in the
1061                          * correct place
1062                          */
1063                         assert(graph->new_mapping[i] == -1);
1064                         graph->new_mapping[i] = target;
1065                 } else if (graph->new_mapping[i - 1] < 0) {
1066                         /*
1067                          * Nothing is to the left.
1068                          * Move to the left by one
1069                          */
1070                         graph->new_mapping[i - 1] = target;
1071                         /*
1072                          * If there isn't already an edge moving horizontally
1073                          * select this one.
1074                          */
1075                         if (horizontal_edge == -1) {
1076                                 int j;
1077                                 horizontal_edge = i;
1078                                 horizontal_edge_target = target;
1079                                 /*
1080                                  * The variable target is the index of the graph
1081                                  * column, and therefore target*2+3 is the
1082                                  * actual screen column of the first horizontal
1083                                  * line.
1084                                  */
1085                                 for (j = (target * 2)+3; j < (i - 2); j += 2)
1086                                         graph->new_mapping[j] = target;
1087                         }
1088                 } else if (graph->new_mapping[i - 1] == target) {
1089                         /*
1090                          * There is a branch line to our left
1091                          * already, and it is our target.  We
1092                          * combine with this line, since we share
1093                          * the same parent commit.
1094                          *
1095                          * We don't have to add anything to the
1096                          * output or new_mapping, since the
1097                          * existing branch line has already taken
1098                          * care of it.
1099                          */
1100                 } else {
1101                         /*
1102                          * There is a branch line to our left,
1103                          * but it isn't our target.  We need to
1104                          * cross over it.
1105                          *
1106                          * The space just to the left of this
1107                          * branch should always be empty.
1108                          *
1109                          * The branch to the left of that space
1110                          * should be our eventual target.
1111                          */
1112                         assert(graph->new_mapping[i - 1] > target);
1113                         assert(graph->new_mapping[i - 2] < 0);
1114                         assert(graph->new_mapping[i - 3] == target);
1115                         graph->new_mapping[i - 2] = target;
1116                         /*
1117                          * Mark this branch as the horizontal edge to
1118                          * prevent any other edges from moving
1119                          * horizontally.
1120                          */
1121                         if (horizontal_edge == -1)
1122                                 horizontal_edge = i;
1123                 }
1124         }
1125
1126         /*
1127          * The new mapping may be 1 smaller than the old mapping
1128          */
1129         if (graph->new_mapping[graph->mapping_size - 1] < 0)
1130                 graph->mapping_size--;
1131
1132         /*
1133          * Output out a line based on the new mapping info
1134          */
1135         for (i = 0; i < graph->mapping_size; i++) {
1136                 int target = graph->new_mapping[i];
1137                 if (target < 0)
1138                         strbuf_addch(sb, ' ');
1139                 else if (target * 2 == i)
1140                         strbuf_write_column(sb, &graph->new_columns[target], '|');
1141                 else if (target == horizontal_edge_target &&
1142                          i != horizontal_edge - 1) {
1143                                 /*
1144                                  * Set the mappings for all but the
1145                                  * first segment to -1 so that they
1146                                  * won't continue into the next line.
1147                                  */
1148                                 if (i != (target * 2)+3)
1149                                         graph->new_mapping[i] = -1;
1150                                 used_horizontal = 1;
1151                         strbuf_write_column(sb, &graph->new_columns[target], '_');
1152                 } else {
1153                         if (used_horizontal && i < horizontal_edge)
1154                                 graph->new_mapping[i] = -1;
1155                         strbuf_write_column(sb, &graph->new_columns[target], '/');
1156
1157                 }
1158         }
1159
1160         graph_pad_horizontally(graph, sb, graph->mapping_size);
1161
1162         /*
1163          * Swap mapping and new_mapping
1164          */
1165         SWAP(graph->mapping, graph->new_mapping);
1166
1167         /*
1168          * If graph->mapping indicates that all of the branch lines
1169          * are already in the correct positions, we are done.
1170          * Otherwise, we need to collapse some branch lines together.
1171          */
1172         if (graph_is_mapping_correct(graph))
1173                 graph_update_state(graph, GRAPH_PADDING);
1174 }
1175
1176 int graph_next_line(struct git_graph *graph, struct strbuf *sb)
1177 {
1178         switch (graph->state) {
1179         case GRAPH_PADDING:
1180                 graph_output_padding_line(graph, sb);
1181                 return 0;
1182         case GRAPH_SKIP:
1183                 graph_output_skip_line(graph, sb);
1184                 return 0;
1185         case GRAPH_PRE_COMMIT:
1186                 graph_output_pre_commit_line(graph, sb);
1187                 return 0;
1188         case GRAPH_COMMIT:
1189                 graph_output_commit_line(graph, sb);
1190                 return 1;
1191         case GRAPH_POST_MERGE:
1192                 graph_output_post_merge_line(graph, sb);
1193                 return 0;
1194         case GRAPH_COLLAPSING:
1195                 graph_output_collapsing_line(graph, sb);
1196                 return 0;
1197         }
1198
1199         assert(0);
1200         return 0;
1201 }
1202
1203 static void graph_padding_line(struct git_graph *graph, struct strbuf *sb)
1204 {
1205         int i;
1206         int chars_written = 0;
1207
1208         if (graph->state != GRAPH_COMMIT) {
1209                 graph_next_line(graph, sb);
1210                 return;
1211         }
1212
1213         /*
1214          * Output the row containing this commit
1215          * Iterate up to and including graph->num_columns,
1216          * since the current commit may not be in any of the existing
1217          * columns.  (This happens when the current commit doesn't have any
1218          * children that we have already processed.)
1219          */
1220         for (i = 0; i < graph->num_columns; i++) {
1221                 struct column *col = &graph->columns[i];
1222
1223                 strbuf_write_column(sb, col, '|');
1224                 chars_written++;
1225
1226                 if (col->commit == graph->commit && graph->num_parents > 2) {
1227                         int len = (graph->num_parents - 2) * 2;
1228                         strbuf_addchars(sb, ' ', len);
1229                         chars_written += len;
1230                 } else {
1231                         strbuf_addch(sb, ' ');
1232                         chars_written++;
1233                 }
1234         }
1235
1236         graph_pad_horizontally(graph, sb, chars_written);
1237
1238         /*
1239          * Update graph->prev_state since we have output a padding line
1240          */
1241         graph->prev_state = GRAPH_PADDING;
1242 }
1243
1244 int graph_is_commit_finished(struct git_graph const *graph)
1245 {
1246         return (graph->state == GRAPH_PADDING);
1247 }
1248
1249 void graph_show_commit(struct git_graph *graph)
1250 {
1251         struct strbuf msgbuf = STRBUF_INIT;
1252         int shown_commit_line = 0;
1253
1254         graph_show_line_prefix(default_diffopt);
1255
1256         if (!graph)
1257                 return;
1258
1259         /*
1260          * When showing a diff of a merge against each of its parents, we
1261          * are called once for each parent without graph_update having been
1262          * called.  In this case, simply output a single padding line.
1263          */
1264         if (graph_is_commit_finished(graph)) {
1265                 graph_show_padding(graph);
1266                 shown_commit_line = 1;
1267         }
1268
1269         while (!shown_commit_line && !graph_is_commit_finished(graph)) {
1270                 shown_commit_line = graph_next_line(graph, &msgbuf);
1271                 fwrite(msgbuf.buf, sizeof(char), msgbuf.len,
1272                         graph->revs->diffopt.file);
1273                 if (!shown_commit_line) {
1274                         putc('\n', graph->revs->diffopt.file);
1275                         graph_show_line_prefix(&graph->revs->diffopt);
1276                 }
1277                 strbuf_setlen(&msgbuf, 0);
1278         }
1279
1280         strbuf_release(&msgbuf);
1281 }
1282
1283 void graph_show_oneline(struct git_graph *graph)
1284 {
1285         struct strbuf msgbuf = STRBUF_INIT;
1286
1287         graph_show_line_prefix(default_diffopt);
1288
1289         if (!graph)
1290                 return;
1291
1292         graph_next_line(graph, &msgbuf);
1293         fwrite(msgbuf.buf, sizeof(char), msgbuf.len, graph->revs->diffopt.file);
1294         strbuf_release(&msgbuf);
1295 }
1296
1297 void graph_show_padding(struct git_graph *graph)
1298 {
1299         struct strbuf msgbuf = STRBUF_INIT;
1300
1301         graph_show_line_prefix(default_diffopt);
1302
1303         if (!graph)
1304                 return;
1305
1306         graph_padding_line(graph, &msgbuf);
1307         fwrite(msgbuf.buf, sizeof(char), msgbuf.len, graph->revs->diffopt.file);
1308         strbuf_release(&msgbuf);
1309 }
1310
1311 int graph_show_remainder(struct git_graph *graph)
1312 {
1313         struct strbuf msgbuf = STRBUF_INIT;
1314         int shown = 0;
1315
1316         graph_show_line_prefix(default_diffopt);
1317
1318         if (!graph)
1319                 return 0;
1320
1321         if (graph_is_commit_finished(graph))
1322                 return 0;
1323
1324         for (;;) {
1325                 graph_next_line(graph, &msgbuf);
1326                 fwrite(msgbuf.buf, sizeof(char), msgbuf.len,
1327                         graph->revs->diffopt.file);
1328                 strbuf_setlen(&msgbuf, 0);
1329                 shown = 1;
1330
1331                 if (!graph_is_commit_finished(graph)) {
1332                         putc('\n', graph->revs->diffopt.file);
1333                         graph_show_line_prefix(&graph->revs->diffopt);
1334                 } else {
1335                         break;
1336                 }
1337         }
1338         strbuf_release(&msgbuf);
1339
1340         return shown;
1341 }
1342
1343 static void graph_show_strbuf(struct git_graph *graph,
1344                               FILE *file,
1345                               struct strbuf const *sb)
1346 {
1347         char *p;
1348
1349         /*
1350          * Print the strbuf line by line,
1351          * and display the graph info before each line but the first.
1352          */
1353         p = sb->buf;
1354         while (p) {
1355                 size_t len;
1356                 char *next_p = strchr(p, '\n');
1357                 if (next_p) {
1358                         next_p++;
1359                         len = next_p - p;
1360                 } else {
1361                         len = (sb->buf + sb->len) - p;
1362                 }
1363                 fwrite(p, sizeof(char), len, file);
1364                 if (next_p && *next_p != '\0')
1365                         graph_show_oneline(graph);
1366                 p = next_p;
1367         }
1368 }
1369
1370 void graph_show_commit_msg(struct git_graph *graph,
1371                            FILE *file,
1372                            struct strbuf const *sb)
1373 {
1374         int newline_terminated;
1375
1376         /*
1377          * Show the commit message
1378          */
1379         graph_show_strbuf(graph, file, sb);
1380
1381         if (!graph)
1382                 return;
1383
1384         newline_terminated = (sb->len && sb->buf[sb->len - 1] == '\n');
1385
1386         /*
1387          * If there is more output needed for this commit, show it now
1388          */
1389         if (!graph_is_commit_finished(graph)) {
1390                 /*
1391                  * If sb doesn't have a terminating newline, print one now,
1392                  * so we can start the remainder of the graph output on a
1393                  * new line.
1394                  */
1395                 if (!newline_terminated)
1396                         putc('\n', file);
1397
1398                 graph_show_remainder(graph);
1399
1400                 /*
1401                  * If sb ends with a newline, our output should too.
1402                  */
1403                 if (newline_terminated)
1404                         putc('\n', file);
1405         }
1406 }