Prepare "git-merge-tree" for future work
[git/git.git] / merge-tree.c
CommitLineData
492e0759 1#include "cache.h"
1b0c7174 2#include "tree-walk.h"
83788070 3#include "blob.h"
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4
5static const char merge_tree_usage[] = "git-merge-tree <base-tree> <branch1> <branch2>";
6static int resolve_directories = 1;
7
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8struct merge_list {
9 struct merge_list *next;
10 struct merge_list *link; /* other stages for this object */
11
12 unsigned int stage : 2,
13 flags : 30;
14 unsigned int mode;
15 const char *path;
16 struct blob *blob;
17};
18
19static struct merge_list *merge_result, **merge_result_end = &merge_result;
20
21static void add_merge_entry(struct merge_list *entry)
22{
23 *merge_result_end = entry;
24 merge_result_end = &entry->next;
25}
26
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27static void merge_trees(struct tree_desc t[3], const char *base);
28
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29static const char *explanation(struct merge_list *entry)
30{
31 switch (entry->stage) {
32 case 0:
33 return "merged";
34 case 3:
35 return "added in remote";
36 case 2:
37 if (entry->link)
38 return "added in both";
39 return "added in local";
40 }
41
42 /* Existed in base */
43 entry = entry->link;
44 if (!entry)
45 return "removed in both";
46
47 if (entry->link)
48 return "changed in both";
49
50 if (entry->stage == 3)
51 return "removed in local";
52 return "removed in remote";
53}
54
55static void show_result_list(struct merge_list *entry)
56{
57 printf("%s\n", explanation(entry));
58 do {
59 struct merge_list *link = entry->link;
60 static const char *desc[4] = { "result", "base", "our", "their" };
61 printf(" %-6s %o %s %s\n", desc[entry->stage], entry->mode, sha1_to_hex(entry->blob->object.sha1), entry->path);
62 entry = link;
63 } while (entry);
64}
65
66static void show_result(void)
67{
68 struct merge_list *walk;
69
70 walk = merge_result;
71 while (walk) {
72 show_result_list(walk);
73 walk = walk->next;
74 }
75}
76
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77/* An empty entry never compares same, not even to another empty entry */
78static int same_entry(struct name_entry *a, struct name_entry *b)
79{
80 return a->sha1 &&
81 b->sha1 &&
82 !memcmp(a->sha1, b->sha1, 20) &&
83 a->mode == b->mode;
84}
85
83788070 86static struct merge_list *create_entry(unsigned stage, unsigned mode, const unsigned char *sha1, const char *path)
492e0759 87{
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88 struct merge_list *res = xmalloc(sizeof(*res));
89
90 memset(res, 0, sizeof(*res));
91 res->stage = stage;
92 res->path = path;
93 res->mode = mode;
94 res->blob = lookup_blob(sha1);
95 return res;
01df5297
LT
96}
97
98static void resolve(const char *base, struct name_entry *branch1, struct name_entry *result)
99{
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100 struct merge_list *orig, *final;
101 const char *path;
102
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103 /* If it's already branch1, don't bother showing it */
104 if (!branch1)
105 return;
01df5297 106
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107 path = strdup(mkpath("%s%s", base, result->path));
108 orig = create_entry(2, branch1->mode, branch1->sha1, path);
109 final = create_entry(0, result->mode, result->sha1, path);
110
111 final->link = orig;
112
113 add_merge_entry(final);
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114}
115
116static int unresolved_directory(const char *base, struct name_entry n[3])
117{
118 int baselen;
119 char *newbase;
120 struct name_entry *p;
121 struct tree_desc t[3];
122 void *buf0, *buf1, *buf2;
123
124 if (!resolve_directories)
125 return 0;
126 p = n;
127 if (!p->mode) {
128 p++;
129 if (!p->mode)
130 p++;
131 }
132 if (!S_ISDIR(p->mode))
133 return 0;
134 baselen = strlen(base);
135 newbase = xmalloc(baselen + p->pathlen + 2);
136 memcpy(newbase, base, baselen);
137 memcpy(newbase + baselen, p->path, p->pathlen);
138 memcpy(newbase + baselen + p->pathlen, "/", 2);
139
140 buf0 = fill_tree_descriptor(t+0, n[0].sha1);
141 buf1 = fill_tree_descriptor(t+1, n[1].sha1);
142 buf2 = fill_tree_descriptor(t+2, n[2].sha1);
143 merge_trees(t, newbase);
144
145 free(buf0);
146 free(buf1);
147 free(buf2);
148 free(newbase);
149 return 1;
150}
151
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152
153static struct merge_list *link_entry(unsigned stage, const char *base, struct name_entry *n, struct merge_list *entry)
154{
155 const char *path;
156 struct merge_list *link;
157
158 if (!n->mode)
159 return entry;
160 if (entry)
161 path = entry->path;
162 else
163 path = strdup(mkpath("%s%s", base, n->path));
164 link = create_entry(stage, n->mode, n->sha1, path);
165 link->link = entry;
166 return link;
167}
168
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169static void unresolved(const char *base, struct name_entry n[3])
170{
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171 struct merge_list *entry = NULL;
172
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173 if (unresolved_directory(base, n))
174 return;
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175
176 /*
177 * Do them in reverse order so that the resulting link
178 * list has the stages in order - link_entry adds new
179 * links at the front.
180 */
181 entry = link_entry(3, base, n + 2, entry);
182 entry = link_entry(2, base, n + 1, entry);
183 entry = link_entry(1, base, n + 0, entry);
184
185 add_merge_entry(entry);
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186}
187
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188/*
189 * Merge two trees together (t[1] and t[2]), using a common base (t[0])
190 * as the origin.
191 *
192 * This walks the (sorted) trees in lock-step, checking every possible
193 * name. Note that directories automatically sort differently from other
194 * files (see "base_name_compare"), so you'll never see file/directory
195 * conflicts, because they won't ever compare the same.
196 *
197 * IOW, if a directory changes to a filename, it will automatically be
198 * seen as the directory going away, and the filename being created.
199 *
200 * Think of this as a three-way diff.
201 *
202 * The output will be either:
203 * - successful merge
204 * "0 mode sha1 filename"
205 * NOTE NOTE NOTE! FIXME! We really really need to walk the index
206 * in parallel with this too!
207 *
208 * - conflict:
209 * "1 mode sha1 filename"
210 * "2 mode sha1 filename"
211 * "3 mode sha1 filename"
212 * where not all of the 1/2/3 lines may exist, of course.
213 *
214 * The successful merge rules are the same as for the three-way merge
215 * in git-read-tree.
216 */
217static void threeway_callback(int n, unsigned long mask, struct name_entry *entry, const char *base)
218{
219 /* Same in both? */
220 if (same_entry(entry+1, entry+2)) {
221 if (entry[0].sha1) {
222 resolve(base, NULL, entry+1);
223 return;
492e0759 224 }
164dcb97 225 }
492e0759 226
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LT
227 if (same_entry(entry+0, entry+1)) {
228 if (entry[2].sha1 && !S_ISDIR(entry[2].mode)) {
229 resolve(base, entry+1, entry+2);
230 return;
492e0759 231 }
164dcb97 232 }
492e0759 233
164dcb97
LT
234 if (same_entry(entry+0, entry+2)) {
235 if (entry[1].sha1 && !S_ISDIR(entry[1].mode)) {
236 resolve(base, NULL, entry+1);
237 return;
492e0759 238 }
492e0759 239 }
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240
241 unresolved(base, entry);
242}
243
244static void merge_trees(struct tree_desc t[3], const char *base)
245{
246 traverse_trees(3, t, base, threeway_callback);
492e0759
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247}
248
249static void *get_tree_descriptor(struct tree_desc *desc, const char *rev)
250{
251 unsigned char sha1[20];
252 void *buf;
253
31fff305 254 if (get_sha1(rev, sha1))
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LT
255 die("unknown rev %s", rev);
256 buf = fill_tree_descriptor(desc, sha1);
257 if (!buf)
258 die("%s is not a tree", rev);
259 return buf;
260}
261
262int main(int argc, char **argv)
263{
264 struct tree_desc t[3];
265 void *buf1, *buf2, *buf3;
266
267 if (argc < 4)
268 usage(merge_tree_usage);
269
270 buf1 = get_tree_descriptor(t+0, argv[1]);
271 buf2 = get_tree_descriptor(t+1, argv[2]);
272 buf3 = get_tree_descriptor(t+2, argv[3]);
273 merge_trees(t, "");
274 free(buf1);
275 free(buf2);
276 free(buf3);
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277
278 show_result();
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279 return 0;
280}