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