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