Merge branch 'maint'
[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 void graph_insert_into_new_columns(struct git_graph *graph,
241                                           struct commit *commit,
242                                           int *mapping_index)
243 {
244         int i;
245
246         /*
247          * Ignore uinteresting commits
248          */
249         if (!graph_is_interesting(graph, commit))
250                 return;
251
252         /*
253          * If the commit is already in the new_columns list, we don't need to
254          * add it.  Just update the mapping correctly.
255          */
256         for (i = 0; i < graph->num_new_columns; i++) {
257                 if (graph->new_columns[i].commit == commit) {
258                         graph->mapping[*mapping_index] = i;
259                         *mapping_index += 2;
260                         return;
261                 }
262         }
263
264         /*
265          * This commit isn't already in new_columns.  Add it.
266          */
267         graph->new_columns[graph->num_new_columns].commit = commit;
268         graph->mapping[*mapping_index] = graph->num_new_columns;
269         *mapping_index += 2;
270         graph->num_new_columns++;
271 }
272
273 static void graph_update_width(struct git_graph *graph,
274                                int is_commit_in_existing_columns)
275 {
276         /*
277          * Compute the width needed to display the graph for this commit.
278          * This is the maximum width needed for any row.  All other rows
279          * will be padded to this width.
280          *
281          * Compute the number of columns in the widest row:
282          * Count each existing column (graph->num_columns), and each new
283          * column added by this commit.
284          */
285         int max_cols = graph->num_columns + graph->num_parents;
286
287         /*
288          * Even if the current commit has no parents to be printed, it
289          * still takes up a column for itself.
290          */
291         if (graph->num_parents < 1)
292                 max_cols++;
293
294         /*
295          * We added a column for the the current commit as part of
296          * graph->num_parents.  If the current commit was already in
297          * graph->columns, then we have double counted it.
298          */
299         if (is_commit_in_existing_columns)
300                 max_cols--;
301
302         /*
303          * Each column takes up 2 spaces
304          */
305         graph->width = max_cols * 2;
306 }
307
308 static void graph_update_columns(struct git_graph *graph)
309 {
310         struct commit_list *parent;
311         struct column *tmp_columns;
312         int max_new_columns;
313         int mapping_idx;
314         int i, seen_this, is_commit_in_columns;
315
316         /*
317          * Swap graph->columns with graph->new_columns
318          * graph->columns contains the state for the previous commit,
319          * and new_columns now contains the state for our commit.
320          *
321          * We'll re-use the old columns array as storage to compute the new
322          * columns list for the commit after this one.
323          */
324         tmp_columns = graph->columns;
325         graph->columns = graph->new_columns;
326         graph->num_columns = graph->num_new_columns;
327
328         graph->new_columns = tmp_columns;
329         graph->num_new_columns = 0;
330
331         /*
332          * Now update new_columns and mapping with the information for the
333          * commit after this one.
334          *
335          * First, make sure we have enough room.  At most, there will
336          * be graph->num_columns + graph->num_parents columns for the next
337          * commit.
338          */
339         max_new_columns = graph->num_columns + graph->num_parents;
340         graph_ensure_capacity(graph, max_new_columns);
341
342         /*
343          * Clear out graph->mapping
344          */
345         graph->mapping_size = 2 * max_new_columns;
346         for (i = 0; i < graph->mapping_size; i++)
347                 graph->mapping[i] = -1;
348
349         /*
350          * Populate graph->new_columns and graph->mapping
351          *
352          * Some of the parents of this commit may already be in
353          * graph->columns.  If so, graph->new_columns should only contain a
354          * single entry for each such commit.  graph->mapping should
355          * contain information about where each current branch line is
356          * supposed to end up after the collapsing is performed.
357          */
358         seen_this = 0;
359         mapping_idx = 0;
360         is_commit_in_columns = 1;
361         for (i = 0; i <= graph->num_columns; i++) {
362                 struct commit *col_commit;
363                 if (i == graph->num_columns) {
364                         if (seen_this)
365                                 break;
366                         is_commit_in_columns = 0;
367                         col_commit = graph->commit;
368                 } else {
369                         col_commit = graph->columns[i].commit;
370                 }
371
372                 if (col_commit == graph->commit) {
373                         int old_mapping_idx = mapping_idx;
374                         seen_this = 1;
375                         graph->commit_index = i;
376                         for (parent = graph->commit->parents;
377                              parent;
378                              parent = parent->next) {
379                                 graph_insert_into_new_columns(graph,
380                                                               parent->item,
381                                                               &mapping_idx);
382                         }
383                         /*
384                          * We always need to increment mapping_idx by at
385                          * least 2, even if it has no interesting parents.
386                          * The current commit always takes up at least 2
387                          * spaces.
388                          */
389                         if (mapping_idx == old_mapping_idx)
390                                 mapping_idx += 2;
391                 } else {
392                         graph_insert_into_new_columns(graph, col_commit,
393                                                       &mapping_idx);
394                 }
395         }
396
397         /*
398          * Shrink mapping_size to be the minimum necessary
399          */
400         while (graph->mapping_size > 1 &&
401                graph->mapping[graph->mapping_size - 1] < 0)
402                 graph->mapping_size--;
403
404         /*
405          * Compute graph->width for this commit
406          */
407         graph_update_width(graph, is_commit_in_columns);
408 }
409
410 void graph_update(struct git_graph *graph, struct commit *commit)
411 {
412         struct commit_list *parent;
413
414         /*
415          * Set the new commit
416          */
417         graph->commit = commit;
418
419         /*
420          * Count how many interesting parents this commit has
421          */
422         graph->num_parents = 0;
423         for (parent = commit->parents; parent; parent = parent->next) {
424                 if (graph_is_interesting(graph, parent->item))
425                         graph->num_parents++;
426         }
427
428         /*
429          * Store the old commit_index in prev_commit_index.
430          * graph_update_columns() will update graph->commit_index for this
431          * commit.
432          */
433         graph->prev_commit_index = graph->commit_index;
434
435         /*
436          * Call graph_update_columns() to update
437          * columns, new_columns, and mapping.
438          */
439         graph_update_columns(graph);
440
441         graph->expansion_row = 0;
442
443         /*
444          * Update graph->state.
445          * Note that we don't call graph_update_state() here, since
446          * we don't want to update graph->prev_state.  No line for
447          * graph->state was ever printed.
448          *
449          * If the previous commit didn't get to the GRAPH_PADDING state,
450          * it never finished its output.  Goto GRAPH_SKIP, to print out
451          * a line to indicate that portion of the graph is missing.
452          *
453          * If there are 3 or more parents, we may need to print extra rows
454          * before the commit, to expand the branch lines around it and make
455          * room for it.  We need to do this only if there is a branch row
456          * (or more) to the right of this commit.
457          *
458          * If there are less than 3 parents, we can immediately print the
459          * commit line.
460          */
461         if (graph->state != GRAPH_PADDING)
462                 graph->state = GRAPH_SKIP;
463         else if (graph->num_parents >= 3 &&
464                  graph->commit_index < (graph->num_columns - 1))
465                 graph->state = GRAPH_PRE_COMMIT;
466         else
467                 graph->state = GRAPH_COMMIT;
468 }
469
470 static int graph_is_mapping_correct(struct git_graph *graph)
471 {
472         int i;
473
474         /*
475          * The mapping is up to date if each entry is at its target,
476          * or is 1 greater than its target.
477          * (If it is 1 greater than the target, '/' will be printed, so it
478          * will look correct on the next row.)
479          */
480         for (i = 0; i < graph->mapping_size; i++) {
481                 int target = graph->mapping[i];
482                 if (target < 0)
483                         continue;
484                 if (target == (i / 2))
485                         continue;
486                 return 0;
487         }
488
489         return 1;
490 }
491
492 static void graph_pad_horizontally(struct git_graph *graph, struct strbuf *sb)
493 {
494         /*
495          * Add additional spaces to the end of the strbuf, so that all
496          * lines for a particular commit have the same width.
497          *
498          * This way, fields printed to the right of the graph will remain
499          * aligned for the entire commit.
500          */
501         int extra;
502         if (sb->len >= graph->width)
503                 return;
504
505         extra = graph->width - sb->len;
506         strbuf_addf(sb, "%*s", (int) extra, "");
507 }
508
509 static void graph_output_padding_line(struct git_graph *graph,
510                                       struct strbuf *sb)
511 {
512         int i;
513
514         /*
515          * We could conceivable be called with a NULL commit
516          * if our caller has a bug, and invokes graph_next_line()
517          * immediately after graph_init(), without first calling
518          * graph_update().  Return without outputting anything in this
519          * case.
520          */
521         if (!graph->commit)
522                 return;
523
524         /*
525          * Output a padding row, that leaves all branch lines unchanged
526          */
527         for (i = 0; i < graph->num_new_columns; i++) {
528                 strbuf_addstr(sb, "| ");
529         }
530
531         graph_pad_horizontally(graph, sb);
532 }
533
534 static void graph_output_skip_line(struct git_graph *graph, struct strbuf *sb)
535 {
536         /*
537          * Output an ellipsis to indicate that a portion
538          * of the graph is missing.
539          */
540         strbuf_addstr(sb, "...");
541         graph_pad_horizontally(graph, sb);
542
543         if (graph->num_parents >= 3 &&
544             graph->commit_index < (graph->num_columns - 1))
545                 graph_update_state(graph, GRAPH_PRE_COMMIT);
546         else
547                 graph_update_state(graph, GRAPH_COMMIT);
548 }
549
550 static void graph_output_pre_commit_line(struct git_graph *graph,
551                                          struct strbuf *sb)
552 {
553         int num_expansion_rows;
554         int i, seen_this;
555
556         /*
557          * This function formats a row that increases the space around a commit
558          * with multiple parents, to make room for it.  It should only be
559          * called when there are 3 or more parents.
560          *
561          * We need 2 extra rows for every parent over 2.
562          */
563         assert(graph->num_parents >= 3);
564         num_expansion_rows = (graph->num_parents - 2) * 2;
565
566         /*
567          * graph->expansion_row tracks the current expansion row we are on.
568          * It should be in the range [0, num_expansion_rows - 1]
569          */
570         assert(0 <= graph->expansion_row &&
571                graph->expansion_row < num_expansion_rows);
572
573         /*
574          * Output the row
575          */
576         seen_this = 0;
577         for (i = 0; i < graph->num_columns; i++) {
578                 struct column *col = &graph->columns[i];
579                 if (col->commit == graph->commit) {
580                         seen_this = 1;
581                         strbuf_addf(sb, "| %*s", graph->expansion_row, "");
582                 } else if (seen_this && (graph->expansion_row == 0)) {
583                         /*
584                          * This is the first line of the pre-commit output.
585                          * If the previous commit was a merge commit and
586                          * ended in the GRAPH_POST_MERGE state, all branch
587                          * lines after graph->prev_commit_index were
588                          * printed as "\" on the previous line.  Continue
589                          * to print them as "\" on this line.  Otherwise,
590                          * print the branch lines as "|".
591                          */
592                         if (graph->prev_state == GRAPH_POST_MERGE &&
593                             graph->prev_commit_index < i)
594                                 strbuf_addstr(sb, "\\ ");
595                         else
596                                 strbuf_addstr(sb, "| ");
597                 } else if (seen_this && (graph->expansion_row > 0)) {
598                         strbuf_addstr(sb, "\\ ");
599                 } else {
600                         strbuf_addstr(sb, "| ");
601                 }
602         }
603
604         graph_pad_horizontally(graph, sb);
605
606         /*
607          * Increment graph->expansion_row,
608          * and move to state GRAPH_COMMIT if necessary
609          */
610         graph->expansion_row++;
611         if (graph->expansion_row >= num_expansion_rows)
612                 graph_update_state(graph, GRAPH_COMMIT);
613 }
614
615 static void graph_output_commit_char(struct git_graph *graph, struct strbuf *sb)
616 {
617         /*
618          * For boundary commits, print 'o'
619          * (We should only see boundary commits when revs->boundary is set.)
620          */
621         if (graph->commit->object.flags & BOUNDARY) {
622                 assert(graph->revs->boundary);
623                 strbuf_addch(sb, 'o');
624                 return;
625         }
626
627         /*
628          * If revs->left_right is set, print '<' for commits that
629          * come from the left side, and '>' for commits from the right
630          * side.
631          */
632         if (graph->revs && graph->revs->left_right) {
633                 if (graph->commit->object.flags & SYMMETRIC_LEFT)
634                         strbuf_addch(sb, '<');
635                 else
636                         strbuf_addch(sb, '>');
637                 return;
638         }
639
640         /*
641          * Print 'M' for merge commits
642          *
643          * Note that we don't check graph->num_parents to determine if the
644          * commit is a merge, since that only tracks the number of
645          * "interesting" parents.  We want to print 'M' for merge commits
646          * even if they have less than 2 interesting parents.
647          */
648         if (graph->commit->parents != NULL &&
649             graph->commit->parents->next != NULL) {
650                 strbuf_addch(sb, 'M');
651                 return;
652         }
653
654         /*
655          * Print '*' in all other cases
656          */
657         strbuf_addch(sb, '*');
658 }
659
660 void graph_output_commit_line(struct git_graph *graph, struct strbuf *sb)
661 {
662         int seen_this = 0;
663         int i, j;
664
665         /*
666          * Output the row containing this commit
667          * Iterate up to and including graph->num_columns,
668          * since the current commit may not be in any of the existing
669          * columns.  (This happens when the current commit doesn't have any
670          * children that we have already processed.)
671          */
672         seen_this = 0;
673         for (i = 0; i <= graph->num_columns; i++) {
674                 struct commit *col_commit;
675                 if (i == graph->num_columns) {
676                         if (seen_this)
677                                 break;
678                         col_commit = graph->commit;
679                 } else {
680                         col_commit = graph->columns[i].commit;
681                 }
682
683                 if (col_commit == graph->commit) {
684                         seen_this = 1;
685                         graph_output_commit_char(graph, sb);
686
687                         if (graph->num_parents < 3)
688                                 strbuf_addch(sb, ' ');
689                         else {
690                                 int num_dashes =
691                                         ((graph->num_parents - 2) * 2) - 1;
692                                 for (j = 0; j < num_dashes; j++)
693                                         strbuf_addch(sb, '-');
694                                 strbuf_addstr(sb, ". ");
695                         }
696                 } else if (seen_this && (graph->num_parents > 2)) {
697                         strbuf_addstr(sb, "\\ ");
698                 } else if (seen_this && (graph->num_parents == 2)) {
699                         /*
700                          * This is a 2-way merge commit.
701                          * There is no GRAPH_PRE_COMMIT stage for 2-way
702                          * merges, so this is the first line of output
703                          * for this commit.  Check to see what the previous
704                          * line of output was.
705                          *
706                          * If it was GRAPH_POST_MERGE, the branch line
707                          * coming into this commit may have been '\',
708                          * and not '|' or '/'.  If so, output the branch
709                          * line as '\' on this line, instead of '|'.  This
710                          * makes the output look nicer.
711                          */
712                         if (graph->prev_state == GRAPH_POST_MERGE &&
713                             graph->prev_commit_index < i)
714                                 strbuf_addstr(sb, "\\ ");
715                         else
716                                 strbuf_addstr(sb, "| ");
717                 } else {
718                         strbuf_addstr(sb, "| ");
719                 }
720         }
721
722         graph_pad_horizontally(graph, sb);
723
724         /*
725          * Update graph->state
726          */
727         if (graph->num_parents > 1)
728                 graph_update_state(graph, GRAPH_POST_MERGE);
729         else if (graph_is_mapping_correct(graph))
730                 graph_update_state(graph, GRAPH_PADDING);
731         else
732                 graph_update_state(graph, GRAPH_COLLAPSING);
733 }
734
735 void graph_output_post_merge_line(struct git_graph *graph, struct strbuf *sb)
736 {
737         int seen_this = 0;
738         int i, j;
739
740         /*
741          * Output the post-merge row
742          */
743         for (i = 0; i <= graph->num_columns; i++) {
744                 struct commit *col_commit;
745                 if (i == graph->num_columns) {
746                         if (seen_this)
747                                 break;
748                         col_commit = graph->commit;
749                 } else {
750                         col_commit = graph->columns[i].commit;
751                 }
752
753                 if (col_commit == graph->commit) {
754                         seen_this = 1;
755                         strbuf_addch(sb, '|');
756                         for (j = 0; j < graph->num_parents - 1; j++)
757                                 strbuf_addstr(sb, "\\ ");
758                 } else if (seen_this) {
759                         strbuf_addstr(sb, "\\ ");
760                 } else {
761                         strbuf_addstr(sb, "| ");
762                 }
763         }
764
765         graph_pad_horizontally(graph, sb);
766
767         /*
768          * Update graph->state
769          */
770         if (graph_is_mapping_correct(graph))
771                 graph_update_state(graph, GRAPH_PADDING);
772         else
773                 graph_update_state(graph, GRAPH_COLLAPSING);
774 }
775
776 void graph_output_collapsing_line(struct git_graph *graph, struct strbuf *sb)
777 {
778         int i;
779         int *tmp_mapping;
780
781         /*
782          * Clear out the new_mapping array
783          */
784         for (i = 0; i < graph->mapping_size; i++)
785                 graph->new_mapping[i] = -1;
786
787         for (i = 0; i < graph->mapping_size; i++) {
788                 int target = graph->mapping[i];
789                 if (target < 0)
790                         continue;
791
792                 /*
793                  * Since update_columns() always inserts the leftmost
794                  * column first, each branch's target location should
795                  * always be either its current location or to the left of
796                  * its current location.
797                  *
798                  * We never have to move branches to the right.  This makes
799                  * the graph much more legible, since whenever branches
800                  * cross, only one is moving directions.
801                  */
802                 assert(target * 2 <= i);
803
804                 if (target * 2 == i) {
805                         /*
806                          * This column is already in the
807                          * correct place
808                          */
809                         assert(graph->new_mapping[i] == -1);
810                         graph->new_mapping[i] = target;
811                 } else if (graph->new_mapping[i - 1] < 0) {
812                         /*
813                          * Nothing is to the left.
814                          * Move to the left by one
815                          */
816                         graph->new_mapping[i - 1] = target;
817                 } else if (graph->new_mapping[i - 1] == target) {
818                         /*
819                          * There is a branch line to our left
820                          * already, and it is our target.  We
821                          * combine with this line, since we share
822                          * the same parent commit.
823                          *
824                          * We don't have to add anything to the
825                          * output or new_mapping, since the
826                          * existing branch line has already taken
827                          * care of it.
828                          */
829                 } else {
830                         /*
831                          * There is a branch line to our left,
832                          * but it isn't our target.  We need to
833                          * cross over it.
834                          *
835                          * The space just to the left of this
836                          * branch should always be empty.
837                          */
838                         assert(graph->new_mapping[i - 1] > target);
839                         assert(graph->new_mapping[i - 2] < 0);
840                         graph->new_mapping[i - 2] = target;
841                 }
842         }
843
844         /*
845          * The new mapping may be 1 smaller than the old mapping
846          */
847         if (graph->new_mapping[graph->mapping_size - 1] < 0)
848                 graph->mapping_size--;
849
850         /*
851          * Output out a line based on the new mapping info
852          */
853         for (i = 0; i < graph->mapping_size; i++) {
854                 int target = graph->new_mapping[i];
855                 if (target < 0)
856                         strbuf_addch(sb, ' ');
857                 else if (target * 2 == i)
858                         strbuf_addch(sb, '|');
859                 else
860                         strbuf_addch(sb, '/');
861         }
862
863         graph_pad_horizontally(graph, sb);
864
865         /*
866          * Swap mapping and new_mapping
867          */
868         tmp_mapping = graph->mapping;
869         graph->mapping = graph->new_mapping;
870         graph->new_mapping = tmp_mapping;
871
872         /*
873          * If graph->mapping indicates that all of the branch lines
874          * are already in the correct positions, we are done.
875          * Otherwise, we need to collapse some branch lines together.
876          */
877         if (graph_is_mapping_correct(graph))
878                 graph_update_state(graph, GRAPH_PADDING);
879 }
880
881 int graph_next_line(struct git_graph *graph, struct strbuf *sb)
882 {
883         switch (graph->state) {
884         case GRAPH_PADDING:
885                 graph_output_padding_line(graph, sb);
886                 return 0;
887         case GRAPH_SKIP:
888                 graph_output_skip_line(graph, sb);
889                 return 0;
890         case GRAPH_PRE_COMMIT:
891                 graph_output_pre_commit_line(graph, sb);
892                 return 0;
893         case GRAPH_COMMIT:
894                 graph_output_commit_line(graph, sb);
895                 return 1;
896         case GRAPH_POST_MERGE:
897                 graph_output_post_merge_line(graph, sb);
898                 return 0;
899         case GRAPH_COLLAPSING:
900                 graph_output_collapsing_line(graph, sb);
901                 return 0;
902         }
903
904         assert(0);
905         return 0;
906 }
907
908 void graph_padding_line(struct git_graph *graph, struct strbuf *sb)
909 {
910         int i, j;
911
912         if (graph->state != GRAPH_COMMIT) {
913                 graph_next_line(graph, sb);
914                 return;
915         }
916
917         /*
918          * Output the row containing this commit
919          * Iterate up to and including graph->num_columns,
920          * since the current commit may not be in any of the existing
921          * columns.  (This happens when the current commit doesn't have any
922          * children that we have already processed.)
923          */
924         for (i = 0; i < graph->num_columns; i++) {
925                 struct commit *col_commit = graph->columns[i].commit;
926                 if (col_commit == graph->commit) {
927                         strbuf_addch(sb, '|');
928
929                         if (graph->num_parents < 3)
930                                 strbuf_addch(sb, ' ');
931                         else {
932                                 int num_spaces = ((graph->num_parents - 2) * 2);
933                                 for (j = 0; j < num_spaces; j++)
934                                         strbuf_addch(sb, ' ');
935                         }
936                 } else {
937                         strbuf_addstr(sb, "| ");
938                 }
939         }
940
941         graph_pad_horizontally(graph, sb);
942
943         /*
944          * Update graph->prev_state since we have output a padding line
945          */
946         graph->prev_state = GRAPH_PADDING;
947 }
948
949 int graph_is_commit_finished(struct git_graph const *graph)
950 {
951         return (graph->state == GRAPH_PADDING);
952 }
953
954 void graph_show_commit(struct git_graph *graph)
955 {
956         struct strbuf msgbuf;
957         int shown_commit_line = 0;
958
959         if (!graph)
960                 return;
961
962         strbuf_init(&msgbuf, 0);
963
964         while (!shown_commit_line) {
965                 shown_commit_line = graph_next_line(graph, &msgbuf);
966                 fwrite(msgbuf.buf, sizeof(char), msgbuf.len, stdout);
967                 if (!shown_commit_line)
968                         putchar('\n');
969                 strbuf_setlen(&msgbuf, 0);
970         }
971
972         strbuf_release(&msgbuf);
973 }
974
975 void graph_show_oneline(struct git_graph *graph)
976 {
977         struct strbuf msgbuf;
978
979         if (!graph)
980                 return;
981
982         strbuf_init(&msgbuf, 0);
983         graph_next_line(graph, &msgbuf);
984         fwrite(msgbuf.buf, sizeof(char), msgbuf.len, stdout);
985         strbuf_release(&msgbuf);
986 }
987
988 void graph_show_padding(struct git_graph *graph)
989 {
990         struct strbuf msgbuf;
991
992         if (!graph)
993                 return;
994
995         strbuf_init(&msgbuf, 0);
996         graph_padding_line(graph, &msgbuf);
997         fwrite(msgbuf.buf, sizeof(char), msgbuf.len, stdout);
998         strbuf_release(&msgbuf);
999 }
1000
1001 int graph_show_remainder(struct git_graph *graph)
1002 {
1003         struct strbuf msgbuf;
1004         int shown = 0;
1005
1006         if (!graph)
1007                 return 0;
1008
1009         if (graph_is_commit_finished(graph))
1010                 return 0;
1011
1012         strbuf_init(&msgbuf, 0);
1013         for (;;) {
1014                 graph_next_line(graph, &msgbuf);
1015                 fwrite(msgbuf.buf, sizeof(char), msgbuf.len, stdout);
1016                 strbuf_setlen(&msgbuf, 0);
1017                 shown = 1;
1018
1019                 if (!graph_is_commit_finished(graph))
1020                         putchar('\n');
1021                 else
1022                         break;
1023         }
1024         strbuf_release(&msgbuf);
1025
1026         return shown;
1027 }
1028
1029
1030 void graph_show_strbuf(struct git_graph *graph, struct strbuf const *sb)
1031 {
1032         char *p;
1033
1034         if (!graph) {
1035                 fwrite(sb->buf, sizeof(char), sb->len, stdout);
1036                 return;
1037         }
1038
1039         /*
1040          * Print the strbuf line by line,
1041          * and display the graph info before each line but the first.
1042          */
1043         p = sb->buf;
1044         while (p) {
1045                 size_t len;
1046                 char *next_p = strchr(p, '\n');
1047                 if (next_p) {
1048                         next_p++;
1049                         len = next_p - p;
1050                 } else {
1051                         len = (sb->buf + sb->len) - p;
1052                 }
1053                 fwrite(p, sizeof(char), len, stdout);
1054                 if (next_p && *next_p != '\0')
1055                         graph_show_oneline(graph);
1056                 p = next_p;
1057         }
1058 }
1059
1060 void graph_show_commit_msg(struct git_graph *graph,
1061                            struct strbuf const *sb)
1062 {
1063         int newline_terminated;
1064
1065         if (!graph) {
1066                 /*
1067                  * If there's no graph, just print the message buffer.
1068                  *
1069                  * The message buffer for CMIT_FMT_ONELINE and
1070                  * CMIT_FMT_USERFORMAT are already missing a terminating
1071                  * newline.  All of the other formats should have it.
1072                  */
1073                 fwrite(sb->buf, sizeof(char), sb->len, stdout);
1074                 return;
1075         }
1076
1077         newline_terminated = (sb->len && sb->buf[sb->len - 1] == '\n');
1078
1079         /*
1080          * Show the commit message
1081          */
1082         graph_show_strbuf(graph, sb);
1083
1084         /*
1085          * If there is more output needed for this commit, show it now
1086          */
1087         if (!graph_is_commit_finished(graph)) {
1088                 /*
1089                  * If sb doesn't have a terminating newline, print one now,
1090                  * so we can start the remainder of the graph output on a
1091                  * new line.
1092                  */
1093                 if (!newline_terminated)
1094                         putchar('\n');
1095
1096                 graph_show_remainder(graph);
1097
1098                 /*
1099                  * If sb ends with a newline, our output should too.
1100                  */
1101                 if (newline_terminated)
1102                         putchar('\n');
1103         }
1104 }