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