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chromium / external / github.com / git / git / refs/tags/v1.0.11 / . / merge-base.c
blob: e73fca7453e8141b3f371a1aeba483c9ed946ccc [file] [log] [blame]
Daniel Barkalowb5039db2005-04-18 18:39:48[diff] [blame]1#include <stdlib.h>
Linus Torvalds66834632005-04-17 19:18:17[diff] [blame]2#include "cache.h"
Daniel Barkalowb5039db2005-04-18 18:39:48[diff] [blame]3#include "commit.h"
Linus Torvalds66834632005-04-17 19:18:17[diff] [blame]4
Linus Torvalds0b9442d2005-08-10 23:26:32[diff] [blame]5#define PARENT1 1
6#define PARENT2 2
7#define UNINTERESTING 4
8
Junio C Hamanob4ad66b2005-08-12 01:13:55[diff] [blame]9static struct commit *interesting(struct commit_list *list)
Linus Torvalds0b9442d2005-08-10 23:26:32[diff] [blame]10{
11 while (list) {
12 struct commit *commit = list->item;
13 list = list->next;
14 if (commit->object.flags & UNINTERESTING)
15 continue;
Junio C Hamanob4ad66b2005-08-12 01:13:55[diff] [blame]16 return commit;
Linus Torvalds0b9442d2005-08-10 23:26:32[diff] [blame]17 }
Junio C Hamanob4ad66b2005-08-12 01:13:55[diff] [blame]18 return NULL;
Linus Torvalds0b9442d2005-08-10 23:26:32[diff] [blame]19}
20
Junio C Hamanob4ad66b2005-08-12 01:13:55[diff] [blame]21/*
22 * A pathological example of how this thing works.
23 *
24 * Suppose we had this commit graph, where chronologically
25 * the timestamp on the commit are A <= B <= C <= D <= E <= F
26 * and we are trying to figure out the merge base for E and F
27 * commits.
28 *
29 * F
30 * / \
31 * E A D
32 * \ / /
33 * B /
34 * \ /
35 * C
36 *
37 * First we push E and F to list to be processed. E gets bit 1
38 * and F gets bit 2. The list becomes:
39 *
40 * list=F(2) E(1), result=empty
41 *
42 * Then we pop F, the newest commit, from the list. Its flag is 2.
43 * We scan its parents, mark them reachable from the side that F is
44 * reachable from, and push them to the list:
45 *
46 * list=E(1) D(2) A(2), result=empty
47 *
48 * Next pop E and do the same.
49 *
50 * list=D(2) B(1) A(2), result=empty
51 *
52 * Next pop D and do the same.
53 *
54 * list=C(2) B(1) A(2), result=empty
55 *
56 * Next pop C and do the same.
57 *
58 * list=B(1) A(2), result=empty
59 *
60 * Now it is B's turn. We mark its parent, C, reachable from B's side,
61 * and push it to the list:
62 *
63 * list=C(3) A(2), result=empty
64 *
65 * Now pop C and notice it has flags==3. It is placed on the result list,
66 * and the list now contains:
67 *
68 * list=A(2), result=C(3)
69 *
70 * We pop A and do the same.
71 *
72 * list=B(3), result=C(3)
73 *
74 * Next, we pop B and something very interesting happens. It has flags==3
75 * so it is also placed on the result list, and its parents are marked
76 * uninteresting, retroactively, and placed back on the list:
77 *
78 * list=C(7), result=C(7) B(3)
79 *
80 * Now, list does not have any interesting commit. So we find the newest
81 * commit from the result list that is not marked uninteresting. Which is
82 * commit B.
Junio C Hamanoed9a5402005-11-11 01:21:54[diff] [blame]83 *
84 *
85 * Another pathological example how this thing can fail to mark an ancestor
86 * of a merge base as UNINTERESTING without the postprocessing phase.
87 *
88 * 2
89 * H
90 * 1 / \
91 * G A \
92 * |\ / \
93 * | B \
94 * | \ \
95 * \ C F
96 * \ \ /
97 * \ D /
98 * \ | /
99 * \| /
100 * E
101 *
102 * list A B C D E F G H
103 * G1 H2 - - - - - - 1 2
104 * H2 E1 B1 - 1 - - 1 - 1 2
105 * F2 E1 B1 A2 2 1 - - 1 2 1 2
106 * E3 B1 A2 2 1 - - 3 2 1 2
107 * B1 A2 2 1 - - 3 2 1 2
108 * C1 A2 2 1 1 - 3 2 1 2
109 * D1 A2 2 1 1 1 3 2 1 2
110 * A2 2 1 1 1 3 2 1 2
111 * B3 2 3 1 1 3 2 1 2
112 * C7 2 3 7 1 3 2 1 2
113 *
114 * At this point, unfortunately, everybody in the list is
115 * uninteresting, so we fail to complete the following two
116 * steps to fully marking uninteresting commits.
117 *
118 * D7 2 3 7 7 3 2 1 2
119 * E7 2 3 7 7 7 2 1 2
120 *
121 * and we end up showing E as an interesting merge base.
Junio C Hamanob4ad66b2005-08-12 01:13:55[diff] [blame]122 */
123
Junio C Hamano9585e402005-08-24 04:08:59[diff] [blame]124static int show_all = 0;
125
Junio C Hamano9e5f4a52005-11-11 06:41:44[diff] [blame]126static void mark_reachable_commits(struct commit_list *result,
127 struct commit_list *list)
128{
129 struct commit_list *tmp;
130
131 /*
132 * Postprocess to fully contaminate the well.
133 */
134 for (tmp = result; tmp; tmp = tmp->next) {
135 struct commit *c = tmp->item;
136 /* Reinject uninteresting ones to list,
137 * so we can scan their parents.
138 */
139 if (c->object.flags & UNINTERESTING)
140 commit_list_insert(c, &list);
141 }
142 while (list) {
143 struct commit *c = list->item;
144 struct commit_list *parents;
145
146 tmp = list;
147 list = list->next;
148 free(tmp);
149
150 /* Anything taken out of the list is uninteresting, so
151 * mark all its parents uninteresting. We do not
152 * parse new ones (we already parsed all the relevant
153 * ones).
154 */
155 parents = c->parents;
156 while (parents) {
157 struct commit *p = parents->item;
158 parents = parents->next;
159 if (!(p->object.flags & UNINTERESTING)) {
160 p->object.flags |= UNINTERESTING;
161 commit_list_insert(p, &list);
162 }
163 }
164 }
165}
166
Junio C Hamano9585e402005-08-24 04:08:59[diff] [blame]167static int merge_base(struct commit *rev1, struct commit *rev2)
Linus Torvalds66834632005-04-17 19:18:17[diff] [blame]168{
Linus Torvalds4f7eb2e2005-07-30 22:10:20[diff] [blame]169 struct commit_list *list = NULL;
170 struct commit_list *result = NULL;
Junio C Hamanoed9a5402005-11-11 01:21:54[diff] [blame]171 struct commit_list *tmp = NULL;
Linus Torvalds66834632005-04-17 19:18:17[diff] [blame]172
Junio C Hamano9585e402005-08-24 04:08:59[diff] [blame]173 if (rev1 == rev2) {
174 printf("%s\n", sha1_to_hex(rev1->object.sha1));
175 return 0;
176 }
Daniel Barkalowb5039db2005-04-18 18:39:48[diff] [blame]177
Daniel Barkalowb6b15db32005-04-24 01:47:23[diff] [blame]178 parse_commit(rev1);
179 parse_commit(rev2);
Daniel Barkalowb5039db2005-04-18 18:39:48[diff] [blame]180
Linus Torvalds4f7eb2e2005-07-30 22:10:20[diff] [blame]181 rev1->object.flags |= 1;
182 rev2->object.flags |= 2;
183 insert_by_date(rev1, &list);
184 insert_by_date(rev2, &list);
185
Linus Torvalds0b9442d2005-08-10 23:26:32[diff] [blame]186 while (interesting(list)) {
Linus Torvalds4f7eb2e2005-07-30 22:10:20[diff] [blame]187 struct commit *commit = list->item;
Junio C Hamanoed9a5402005-11-11 01:21:54[diff] [blame]188 struct commit_list *parents;
Linus Torvalds0b9442d2005-08-10 23:26:32[diff] [blame]189 int flags = commit->object.flags & 7;
Linus Torvalds4f7eb2e2005-07-30 22:10:20[diff] [blame]190
Junio C Hamanoed9a5402005-11-11 01:21:54[diff] [blame]191 tmp = list;
Linus Torvalds4f7eb2e2005-07-30 22:10:20[diff] [blame]192 list = list->next;
193 free(tmp);
Linus Torvalds0b9442d2005-08-10 23:26:32[diff] [blame]194 if (flags == 3) {
Linus Torvalds4f7eb2e2005-07-30 22:10:20[diff] [blame]195 insert_by_date(commit, &result);
Linus Torvalds0b9442d2005-08-10 23:26:32[diff] [blame]196
Junio C Hamano9585e402005-08-24 04:08:59[diff] [blame]197 /* Mark parents of a found merge uninteresting */
Linus Torvalds0b9442d2005-08-10 23:26:32[diff] [blame]198 flags |= UNINTERESTING;
Linus Torvalds66834632005-04-17 19:18:17[diff] [blame]199 }
Linus Torvalds4f7eb2e2005-07-30 22:10:20[diff] [blame]200 parents = commit->parents;
201 while (parents) {
202 struct commit *p = parents->item;
203 parents = parents->next;
204 if ((p->object.flags & flags) == flags)
205 continue;
206 parse_commit(p);
207 p->object.flags |= flags;
208 insert_by_date(p, &list);
Daniel Barkalowb5039db2005-04-18 18:39:48[diff] [blame]209 }
Linus Torvalds66834632005-04-17 19:18:17[diff] [blame]210 }
Junio C Hamano9585e402005-08-24 04:08:59[diff] [blame]211
212 if (!result)
213 return 1;
214
Junio C Hamano9e5f4a52005-11-11 06:41:44[diff] [blame]215 if (result->next && list)
216 mark_reachable_commits(result, list);
Junio C Hamanoed9a5402005-11-11 01:21:54[diff] [blame]217
Junio C Hamano9585e402005-08-24 04:08:59[diff] [blame]218 while (result) {
219 struct commit *commit = result->item;
220 result = result->next;
221 if (commit->object.flags & UNINTERESTING)
222 continue;
223 printf("%s\n", sha1_to_hex(commit->object.sha1));
224 if (!show_all)
225 return 0;
226 commit->object.flags |= UNINTERESTING;
227 }
228 return 0;
Linus Torvalds66834632005-04-17 19:18:17[diff] [blame]229}
230
Junio C Hamano9585e402005-08-24 04:08:59[diff] [blame]231static const char merge_base_usage[] =
232"git-merge-base [--all] <commit-id> <commit-id>";
233
Linus Torvalds66834632005-04-17 19:18:17[diff] [blame]234int main(int argc, char **argv)
235{
Junio C Hamano9585e402005-08-24 04:08:59[diff] [blame]236 struct commit *rev1, *rev2;
Daniel Barkalowb5039db2005-04-18 18:39:48[diff] [blame]237 unsigned char rev1key[20], rev2key[20];
Linus Torvalds66834632005-04-17 19:18:17[diff] [blame]238
Junio C Hamano53228a52005-11-26 08:50:02[diff] [blame]239 setup_git_directory();
240
Junio C Hamano9585e402005-08-24 04:08:59[diff] [blame]241 while (1 < argc && argv[1][0] == '-') {
242 char *arg = argv[1];
243 if (!strcmp(arg, "-a") || !strcmp(arg, "--all"))
244 show_all = 1;
245 else
246 usage(merge_base_usage);
247 argc--; argv++;
248 }
Daniel Barkalowb5039db2005-04-18 18:39:48[diff] [blame]249 if (argc != 3 ||
Linus Torvalds3c249c92005-05-01 23:36:56[diff] [blame]250 get_sha1(argv[1], rev1key) ||
Junio C Hamano9585e402005-08-24 04:08:59[diff] [blame]251 get_sha1(argv[2], rev2key))
252 usage(merge_base_usage);
Linus Torvalds9b632be2005-05-18 23:16:51[diff] [blame]253 rev1 = lookup_commit_reference(rev1key);
254 rev2 = lookup_commit_reference(rev2key);
Linus Torvalds4f7eb2e2005-07-30 22:10:20[diff] [blame]255 if (!rev1 || !rev2)
256 return 1;
Junio C Hamano9585e402005-08-24 04:08:59[diff] [blame]257 return merge_base(rev1, rev2);
Linus Torvalds66834632005-04-17 19:18:17[diff] [blame]258}