Merge fixes early for next maint series.
[git] / merge-tree.c
1 #include "cache.h"
2 #include "diff.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 static void *fill_tree_descriptor(struct tree_desc *desc, const unsigned char *sha1)
10 {
11         unsigned long size = 0;
12         void *buf = NULL;
13
14         if (sha1) {
15                 buf = read_object_with_reference(sha1, "tree", &size, NULL);
16                 if (!buf)
17                         die("unable to read tree %s", sha1_to_hex(sha1));
18         }
19         desc->size = size;
20         desc->buf = buf;
21         return buf;
22 }
23
24 struct name_entry {
25         const unsigned char *sha1;
26         const char *path;
27         unsigned int mode;
28         int pathlen;
29 };
30
31 static void entry_clear(struct name_entry *a)
32 {
33         memset(a, 0, sizeof(*a));
34 }
35
36 static int entry_compare(struct name_entry *a, struct name_entry *b)
37 {
38         return base_name_compare(
39                         a->path, a->pathlen, a->mode,
40                         b->path, b->pathlen, b->mode);
41 }
42
43 static void entry_extract(struct tree_desc *t, struct name_entry *a)
44 {
45         a->sha1 = tree_entry_extract(t, &a->path, &a->mode);
46         a->pathlen = strlen(a->path);
47 }
48
49 /* An empty entry never compares same, not even to another empty entry */
50 static int same_entry(struct name_entry *a, struct name_entry *b)
51 {
52         return  a->sha1 &&
53                 b->sha1 &&
54                 !memcmp(a->sha1, b->sha1, 20) &&
55                 a->mode == b->mode;
56 }
57
58 static const char *sha1_to_hex_zero(const unsigned char *sha1)
59 {
60         if (sha1)
61                 return sha1_to_hex(sha1);
62         return "0000000000000000000000000000000000000000";
63 }
64
65 static void resolve(const char *base, struct name_entry *branch1, struct name_entry *result)
66 {
67         char branch1_sha1[50];
68
69         /* If it's already branch1, don't bother showing it */
70         if (!branch1)
71                 return;
72         memcpy(branch1_sha1, sha1_to_hex_zero(branch1->sha1), 41);
73
74         printf("0 %06o->%06o %s->%s %s%s\n",
75                 branch1->mode, result->mode,
76                 branch1_sha1, sha1_to_hex_zero(result->sha1),
77                 base, result->path);
78 }
79
80 static int unresolved_directory(const char *base, struct name_entry n[3])
81 {
82         int baselen;
83         char *newbase;
84         struct name_entry *p;
85         struct tree_desc t[3];
86         void *buf0, *buf1, *buf2;
87
88         if (!resolve_directories)
89                 return 0;
90         p = n;
91         if (!p->mode) {
92                 p++;
93                 if (!p->mode)
94                         p++;
95         }
96         if (!S_ISDIR(p->mode))
97                 return 0;
98         baselen = strlen(base);
99         newbase = xmalloc(baselen + p->pathlen + 2);
100         memcpy(newbase, base, baselen);
101         memcpy(newbase + baselen, p->path, p->pathlen);
102         memcpy(newbase + baselen + p->pathlen, "/", 2);
103
104         buf0 = fill_tree_descriptor(t+0, n[0].sha1);
105         buf1 = fill_tree_descriptor(t+1, n[1].sha1);
106         buf2 = fill_tree_descriptor(t+2, n[2].sha1);
107         merge_trees(t, newbase);
108
109         free(buf0);
110         free(buf1);
111         free(buf2);
112         free(newbase);
113         return 1;
114 }
115
116 static void unresolved(const char *base, struct name_entry n[3])
117 {
118         if (unresolved_directory(base, n))
119                 return;
120         if (n[0].sha1)
121                 printf("1 %06o %s %s%s\n", n[0].mode, sha1_to_hex(n[0].sha1), base, n[0].path);
122         if (n[1].sha1)
123                 printf("2 %06o %s %s%s\n", n[1].mode, sha1_to_hex(n[1].sha1), base, n[1].path);
124         if (n[2].sha1)
125                 printf("3 %06o %s %s%s\n", n[2].mode, sha1_to_hex(n[2].sha1), base, n[2].path);
126 }
127
128 typedef void (*traverse_callback_t)(int n, unsigned long mask, struct name_entry *entry, const char *base);
129
130 static void traverse_trees(int n, struct tree_desc *t, const char *base, traverse_callback_t callback)
131 {
132         struct name_entry *entry = xmalloc(n*sizeof(*entry));
133
134         for (;;) {
135                 struct name_entry entry[3];
136                 unsigned long mask = 0;
137                 int i, last;
138
139                 last = -1;
140                 for (i = 0; i < n; i++) {
141                         if (!t[i].size)
142                                 continue;
143                         entry_extract(t+i, entry+i);
144                         if (last >= 0) {
145                                 int cmp = entry_compare(entry+i, entry+last);
146
147                                 /*
148                                  * Is the new name bigger than the old one?
149                                  * Ignore it
150                                  */
151                                 if (cmp > 0)
152                                         continue;
153                                 /*
154                                  * Is the new name smaller than the old one?
155                                  * Ignore all old ones
156                                  */
157                                 if (cmp < 0)
158                                         mask = 0;
159                         }
160                         mask |= 1ul << i;
161                         last = i;
162                 }
163                 if (!mask)
164                         break;
165
166                 /*
167                  * Update the tree entries we've walked, and clear
168                  * all the unused name-entries.
169                  */
170                 for (i = 0; i < n; i++) {
171                         if (mask & (1ul << i)) {
172                                 update_tree_entry(t+i);
173                                 continue;
174                         }
175                         entry_clear(entry + i);
176                 }
177                 callback(n, mask, entry, base);
178         }
179         free(entry);
180 }
181
182 /*
183  * Merge two trees together (t[1] and t[2]), using a common base (t[0])
184  * as the origin.
185  *
186  * This walks the (sorted) trees in lock-step, checking every possible
187  * name. Note that directories automatically sort differently from other
188  * files (see "base_name_compare"), so you'll never see file/directory
189  * conflicts, because they won't ever compare the same.
190  *
191  * IOW, if a directory changes to a filename, it will automatically be
192  * seen as the directory going away, and the filename being created.
193  *
194  * Think of this as a three-way diff.
195  *
196  * The output will be either:
197  *  - successful merge
198  *       "0 mode sha1 filename"
199  *    NOTE NOTE NOTE! FIXME! We really really need to walk the index
200  *    in parallel with this too!
201  *
202  *  - conflict:
203  *      "1 mode sha1 filename"
204  *      "2 mode sha1 filename"
205  *      "3 mode sha1 filename"
206  *    where not all of the 1/2/3 lines may exist, of course.
207  *
208  * The successful merge rules are the same as for the three-way merge
209  * in git-read-tree.
210  */
211 static void threeway_callback(int n, unsigned long mask, struct name_entry *entry, const char *base)
212 {
213         /* Same in both? */
214         if (same_entry(entry+1, entry+2)) {
215                 if (entry[0].sha1) {
216                         resolve(base, NULL, entry+1);
217                         return;
218                 }
219         }
220
221         if (same_entry(entry+0, entry+1)) {
222                 if (entry[2].sha1 && !S_ISDIR(entry[2].mode)) {
223                         resolve(base, entry+1, entry+2);
224                         return;
225                 }
226         }
227
228         if (same_entry(entry+0, entry+2)) {
229                 if (entry[1].sha1 && !S_ISDIR(entry[1].mode)) {
230                         resolve(base, NULL, entry+1);
231                         return;
232                 }
233         }
234
235         unresolved(base, entry);
236 }
237
238 static void merge_trees(struct tree_desc t[3], const char *base)
239 {
240         traverse_trees(3, t, base, threeway_callback);
241 }
242
243 static void *get_tree_descriptor(struct tree_desc *desc, const char *rev)
244 {
245         unsigned char sha1[20];
246         void *buf;
247
248         if (get_sha1(rev, sha1) < 0)
249                 die("unknown rev %s", rev);
250         buf = fill_tree_descriptor(desc, sha1);
251         if (!buf)
252                 die("%s is not a tree", rev);
253         return buf;
254 }
255
256 int main(int argc, char **argv)
257 {
258         struct tree_desc t[3];
259         void *buf1, *buf2, *buf3;
260
261         if (argc < 4)
262                 usage(merge_tree_usage);
263
264         buf1 = get_tree_descriptor(t+0, argv[1]);
265         buf2 = get_tree_descriptor(t+1, argv[2]);
266         buf3 = get_tree_descriptor(t+2, argv[3]);
267         merge_trees(t, "");
268         free(buf1);
269         free(buf2);
270         free(buf3);
271         return 0;
272 }