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