read-cache.c: use xcalloc() not calloc()
[git/git.git] / merge-tree.c
1 #include "cache.h"
2 #include "tree-walk.h"
3
4 static const char merge_tree_usage[] = "git-merge-tree <base-tree> <branch1> <branch2>";
5 static int resolve_directories = 1;
6
7 static void merge_trees(struct tree_desc t[3], const char *base);
8
9 /* An empty entry never compares same, not even to another empty entry */
10 static int same_entry(struct name_entry *a, struct name_entry *b)
11 {
12 return a->sha1 &&
13 b->sha1 &&
14 !memcmp(a->sha1, b->sha1, 20) &&
15 a->mode == b->mode;
16 }
17
18 static const char *sha1_to_hex_zero(const unsigned char *sha1)
19 {
20 if (sha1)
21 return sha1_to_hex(sha1);
22 return "0000000000000000000000000000000000000000";
23 }
24
25 static void resolve(const char *base, struct name_entry *branch1, struct name_entry *result)
26 {
27 char branch1_sha1[50];
28
29 /* If it's already branch1, don't bother showing it */
30 if (!branch1)
31 return;
32 memcpy(branch1_sha1, sha1_to_hex_zero(branch1->sha1), 41);
33
34 printf("0 %06o->%06o %s->%s %s%s\n",
35 branch1->mode, result->mode,
36 branch1_sha1, sha1_to_hex_zero(result->sha1),
37 base, result->path);
38 }
39
40 static int unresolved_directory(const char *base, struct name_entry n[3])
41 {
42 int baselen;
43 char *newbase;
44 struct name_entry *p;
45 struct tree_desc t[3];
46 void *buf0, *buf1, *buf2;
47
48 if (!resolve_directories)
49 return 0;
50 p = n;
51 if (!p->mode) {
52 p++;
53 if (!p->mode)
54 p++;
55 }
56 if (!S_ISDIR(p->mode))
57 return 0;
58 baselen = strlen(base);
59 newbase = xmalloc(baselen + p->pathlen + 2);
60 memcpy(newbase, base, baselen);
61 memcpy(newbase + baselen, p->path, p->pathlen);
62 memcpy(newbase + baselen + p->pathlen, "/", 2);
63
64 buf0 = fill_tree_descriptor(t+0, n[0].sha1);
65 buf1 = fill_tree_descriptor(t+1, n[1].sha1);
66 buf2 = fill_tree_descriptor(t+2, n[2].sha1);
67 merge_trees(t, newbase);
68
69 free(buf0);
70 free(buf1);
71 free(buf2);
72 free(newbase);
73 return 1;
74 }
75
76 static void unresolved(const char *base, struct name_entry n[3])
77 {
78 if (unresolved_directory(base, n))
79 return;
80 if (n[0].sha1)
81 printf("1 %06o %s %s%s\n", n[0].mode, sha1_to_hex(n[0].sha1), base, n[0].path);
82 if (n[1].sha1)
83 printf("2 %06o %s %s%s\n", n[1].mode, sha1_to_hex(n[1].sha1), base, n[1].path);
84 if (n[2].sha1)
85 printf("3 %06o %s %s%s\n", n[2].mode, sha1_to_hex(n[2].sha1), base, n[2].path);
86 }
87
88 /*
89 * Merge two trees together (t[1] and t[2]), using a common base (t[0])
90 * as the origin.
91 *
92 * This walks the (sorted) trees in lock-step, checking every possible
93 * name. Note that directories automatically sort differently from other
94 * files (see "base_name_compare"), so you'll never see file/directory
95 * conflicts, because they won't ever compare the same.
96 *
97 * IOW, if a directory changes to a filename, it will automatically be
98 * seen as the directory going away, and the filename being created.
99 *
100 * Think of this as a three-way diff.
101 *
102 * The output will be either:
103 * - successful merge
104 * "0 mode sha1 filename"
105 * NOTE NOTE NOTE! FIXME! We really really need to walk the index
106 * in parallel with this too!
107 *
108 * - conflict:
109 * "1 mode sha1 filename"
110 * "2 mode sha1 filename"
111 * "3 mode sha1 filename"
112 * where not all of the 1/2/3 lines may exist, of course.
113 *
114 * The successful merge rules are the same as for the three-way merge
115 * in git-read-tree.
116 */
117 static void threeway_callback(int n, unsigned long mask, struct name_entry *entry, const char *base)
118 {
119 /* Same in both? */
120 if (same_entry(entry+1, entry+2)) {
121 if (entry[0].sha1) {
122 resolve(base, NULL, entry+1);
123 return;
124 }
125 }
126
127 if (same_entry(entry+0, entry+1)) {
128 if (entry[2].sha1 && !S_ISDIR(entry[2].mode)) {
129 resolve(base, entry+1, entry+2);
130 return;
131 }
132 }
133
134 if (same_entry(entry+0, entry+2)) {
135 if (entry[1].sha1 && !S_ISDIR(entry[1].mode)) {
136 resolve(base, NULL, entry+1);
137 return;
138 }
139 }
140
141 unresolved(base, entry);
142 }
143
144 static void merge_trees(struct tree_desc t[3], const char *base)
145 {
146 traverse_trees(3, t, base, threeway_callback);
147 }
148
149 static void *get_tree_descriptor(struct tree_desc *desc, const char *rev)
150 {
151 unsigned char sha1[20];
152 void *buf;
153
154 if (get_sha1(rev, sha1))
155 die("unknown rev %s", rev);
156 buf = fill_tree_descriptor(desc, sha1);
157 if (!buf)
158 die("%s is not a tree", rev);
159 return buf;
160 }
161
162 int main(int argc, char **argv)
163 {
164 struct tree_desc t[3];
165 void *buf1, *buf2, *buf3;
166
167 if (argc < 4)
168 usage(merge_tree_usage);
169
170 buf1 = get_tree_descriptor(t+0, argv[1]);
171 buf2 = get_tree_descriptor(t+1, argv[2]);
172 buf3 = get_tree_descriptor(t+2, argv[3]);
173 merge_trees(t, "");
174 free(buf1);
175 free(buf2);
176 free(buf3);
177 return 0;
178 }