[PATCH] Document git-ssh-pull and git-ssh-push
[alt-git.git] / read-tree.c
blob2fb27e9743614bc1f01b4bc4b0b4b96de6d1a1ce
1 /*
2 * GIT - The information manager from hell
4 * Copyright (C) Linus Torvalds, 2005
5 */
6 #include "cache.h"
8 static int stage = 0;
9 static int update = 0;
11 static int unpack_tree(unsigned char *sha1)
13 void *buffer;
14 unsigned long size;
15 int ret;
17 buffer = read_object_with_reference(sha1, "tree", &size, NULL);
18 if (!buffer)
19 return -1;
20 ret = read_tree(buffer, size, stage);
21 free(buffer);
22 return ret;
25 static int path_matches(struct cache_entry *a, struct cache_entry *b)
27 int len = ce_namelen(a);
28 return ce_namelen(b) == len &&
29 !memcmp(a->name, b->name, len);
32 static int same(struct cache_entry *a, struct cache_entry *b)
34 return a->ce_mode == b->ce_mode &&
35 !memcmp(a->sha1, b->sha1, 20);
40 * This removes all trivial merges that don't change the tree
41 * and collapses them to state 0.
43 static struct cache_entry *merge_entries(struct cache_entry *a,
44 struct cache_entry *b,
45 struct cache_entry *c)
48 * Ok, all three entries describe the same
49 * filename, but maybe the contents or file
50 * mode have changed?
52 * The trivial cases end up being the ones where two
53 * out of three files are the same:
54 * - both destinations the same, trivially take either
55 * - one of the destination versions hasn't changed,
56 * take the other.
58 * The "all entries exactly the same" case falls out as
59 * a special case of any of the "two same" cases.
61 * Here "a" is "original", and "b" and "c" are the two
62 * trees we are merging.
64 if (a && b && c) {
65 if (same(b,c))
66 return c;
67 if (same(a,b))
68 return c;
69 if (same(a,c))
70 return b;
72 return NULL;
76 * When a CE gets turned into an unmerged entry, we
77 * want it to be up-to-date
79 static void verify_uptodate(struct cache_entry *ce)
81 struct stat st;
83 if (!lstat(ce->name, &st)) {
84 unsigned changed = ce_match_stat(ce, &st);
85 if (!changed)
86 return;
87 errno = 0;
89 if (errno == ENOENT)
90 return;
91 die("Entry '%s' not uptodate. Cannot merge.", ce->name);
95 * If the old tree contained a CE that isn't even in the
96 * result, that's always a problem, regardless of whether
97 * it's up-to-date or not (ie it can be a file that we
98 * have updated but not committed yet).
100 static void reject_merge(struct cache_entry *ce)
102 die("Entry '%s' would be overwritten by merge. Cannot merge.", ce->name);
105 static int merged_entry(struct cache_entry *merge, struct cache_entry *old, struct cache_entry **dst)
107 merge->ce_flags |= htons(CE_UPDATE);
108 if (old) {
110 * See if we can re-use the old CE directly?
111 * That way we get the uptodate stat info.
113 * This also removes the UPDATE flag on
114 * a match.
116 if (same(old, merge)) {
117 *merge = *old;
118 } else {
119 verify_uptodate(old);
122 merge->ce_flags &= ~htons(CE_STAGEMASK);
123 *dst++ = merge;
124 return 1;
127 static int threeway_merge(struct cache_entry *stages[4], struct cache_entry **dst)
129 struct cache_entry *old = stages[0];
130 struct cache_entry *a = stages[1], *b = stages[2], *c = stages[3];
131 struct cache_entry *merge;
132 int count;
135 * If we have an entry in the index cache ("old"), then we want
136 * to make sure that it matches any entries in stage 2 ("first
137 * branch", aka "b").
139 if (old) {
140 if (!b || !same(old, b))
141 return -1;
143 merge = merge_entries(a, b, c);
144 if (merge)
145 return merged_entry(merge, old, dst);
146 if (old)
147 verify_uptodate(old);
148 count = 0;
149 if (a) { *dst++ = a; count++; }
150 if (b) { *dst++ = b; count++; }
151 if (c) { *dst++ = c; count++; }
152 return count;
156 * Two-way merge.
158 * The rule is:
159 * - every current entry has to match the old tree
160 * - if the current entry matches the new tree, we leave it
161 * as-is. Otherwise we require that it be up-to-date.
163 static int twoway_merge(struct cache_entry **src, struct cache_entry **dst)
165 struct cache_entry *old = src[0];
166 struct cache_entry *a = src[1], *b = src[2];
168 if (src[3])
169 return -1;
171 if (old) {
172 if (!a || !same(old, a))
173 return -1;
175 if (b)
176 return merged_entry(b, old, dst);
177 if (old)
178 verify_uptodate(old);
179 return 0;
183 * One-way merge.
185 * The rule is:
186 * - take the stat information from stage0, take the data from stage1
188 static int oneway_merge(struct cache_entry **src, struct cache_entry **dst)
190 struct cache_entry *old = src[0];
191 struct cache_entry *a = src[1];
193 if (src[2] || src[3])
194 return -1;
196 if (!a)
197 return 0;
198 if (old && same(old, a))
199 *a = *old;
200 a->ce_flags &= ~htons(CE_STAGEMASK);
201 *dst++ = a;
202 return 1;
205 static void check_updates(struct cache_entry **src, int nr)
207 static struct checkout state = {
208 .base_dir = "",
209 .force = 1,
210 .quiet = 1,
211 .refresh_cache = 1,
213 unsigned short mask = htons(CE_UPDATE);
214 while (nr--) {
215 struct cache_entry *ce = *src++;
216 if (ce->ce_flags & mask) {
217 ce->ce_flags &= ~mask;
218 if (update)
219 checkout_entry(ce, &state);
224 typedef int (*merge_fn_t)(struct cache_entry **, struct cache_entry **);
226 static void merge_cache(struct cache_entry **src, int nr, merge_fn_t fn)
228 struct cache_entry **dst = src;
230 while (nr) {
231 int entries;
232 struct cache_entry *name, *ce, *stages[4] = { NULL, };
234 name = ce = *src;
235 for (;;) {
236 int stage = ce_stage(ce);
237 stages[stage] = ce;
238 ce = *++src;
239 active_nr--;
240 if (!--nr)
241 break;
242 if (!path_matches(ce, name))
243 break;
246 entries = fn(stages, dst);
247 if (entries < 0)
248 reject_merge(name);
249 dst += entries;
250 active_nr += entries;
252 check_updates(active_cache, active_nr);
255 static char *read_tree_usage = "git-read-tree (<sha> | -m <sha1> [<sha2> [<sha3>]])";
257 static struct cache_file cache_file;
259 int main(int argc, char **argv)
261 int i, newfd, merge;
262 unsigned char sha1[20];
264 newfd = hold_index_file_for_update(&cache_file, get_index_file());
265 if (newfd < 0)
266 die("unable to create new cachefile");
268 merge = 0;
269 for (i = 1; i < argc; i++) {
270 const char *arg = argv[i];
272 /* "-u" means "update", meaning that a merge will update the working directory */
273 if (!strcmp(arg, "-u")) {
274 update = 1;
275 continue;
278 /* "-m" stands for "merge", meaning we start in stage 1 */
279 if (!strcmp(arg, "-m")) {
280 int i;
281 if (stage)
282 die("-m needs to come first");
283 read_cache();
284 for (i = 0; i < active_nr; i++) {
285 if (ce_stage(active_cache[i]))
286 die("you need to resolve your current index first");
288 stage = 1;
289 merge = 1;
290 continue;
292 if (get_sha1(arg, sha1) < 0)
293 usage(read_tree_usage);
294 if (stage > 3)
295 usage(read_tree_usage);
296 if (unpack_tree(sha1) < 0)
297 die("failed to unpack tree object %s", arg);
298 stage++;
300 if (merge) {
301 static const merge_fn_t merge_function[] = {
302 [1] = oneway_merge,
303 [2] = twoway_merge,
304 [3] = threeway_merge,
306 if (stage < 2 || stage > 4)
307 die("just how do you expect me to merge %d trees?", stage-1);
308 merge_cache(active_cache, active_nr, merge_function[stage-1]);
310 if (write_cache(newfd, active_cache, active_nr) ||
311 commit_index_file(&cache_file))
312 die("unable to write new index file");
313 return 0;