[PATCH] Rename and extend read_tree_with_tree_or_commit_sha1
[git/git.git] / read-tree.c
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8bc9a0c7
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1/*
2 * GIT - The information manager from hell
3 *
4 * Copyright (C) Linus Torvalds, 2005
5 */
e83c5163
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6#include "cache.h"
7
d99082e0
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8static int stage = 0;
9
94537c78 10static int unpack_tree(unsigned char *sha1)
b12ec373
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11{
12 void *buffer;
13 unsigned long size;
14
40469ee9 15 buffer = read_object_with_reference(sha1, "tree", &size, 0);
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16 if (!buffer)
17 return -1;
94537c78 18 return read_tree(buffer, size, stage);
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19}
20
bb233d69 21static char *lockfile_name;
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22
23static void remove_lock_file(void)
24{
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25 if (lockfile_name)
26 unlink(lockfile_name);
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27}
28
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29static int path_matches(struct cache_entry *a, struct cache_entry *b)
30{
31 int len = ce_namelen(a);
32 return ce_namelen(b) == len &&
33 !memcmp(a->name, b->name, len);
34}
35
43f91266
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36static int same(struct cache_entry *a, struct cache_entry *b)
37{
38 return a->ce_mode == b->ce_mode &&
39 !memcmp(a->sha1, b->sha1, 20);
40}
41
42
d99082e0 43/*
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44 * This removes all trivial merges that don't change the tree
45 * and collapses them to state 0.
d99082e0 46 *
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47 * _Any_ other merge is left to user policy. That includes "both
48 * created the same file", and "both removed the same file" - which are
49 * trivial, but the user might still want to _note_ it.
d99082e0 50 */
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51static struct cache_entry *merge_entries(struct cache_entry *a,
52 struct cache_entry *b,
53 struct cache_entry *c)
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54{
55 int len = ce_namelen(a);
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56
57 /*
58 * Are they all the same filename? We won't do
59 * any name merging
60 */
61 if (ce_namelen(b) != len ||
62 ce_namelen(c) != len ||
63 memcmp(a->name, b->name, len) ||
64 memcmp(a->name, c->name, len))
65 return NULL;
66
67 /*
68 * Ok, all three entries describe the same
69 * filename, but maybe the contents or file
70 * mode have changed?
71 *
72 * The trivial cases end up being the ones where two
73 * out of three files are the same:
74 * - both destinations the same, trivially take either
75 * - one of the destination versions hasn't changed,
76 * take the other.
77 *
78 * The "all entries exactly the same" case falls out as
79 * a special case of any of the "two same" cases.
80 *
81 * Here "a" is "original", and "b" and "c" are the two
82 * trees we are merging.
83 */
84 if (same(b,c))
85 return c;
86 if (same(a,b))
87 return c;
88 if (same(a,c))
89 return b;
90 return NULL;
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91}
92
93static void trivially_merge_cache(struct cache_entry **src, int nr)
94{
ca016f0e 95 static struct cache_entry null_entry;
d99082e0 96 struct cache_entry **dst = src;
ca016f0e 97 struct cache_entry *old = &null_entry;
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98
99 while (nr) {
43f91266 100 struct cache_entry *ce, *result;
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101
102 ce = src[0];
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103
104 /* We throw away original cache entries except for the stat information */
105 if (!ce_stage(ce)) {
106 old = ce;
107 src++;
108 nr--;
109 active_nr--;
110 continue;
111 }
43f91266 112 if (nr > 2 && (result = merge_entries(ce, src[1], src[2])) != NULL) {
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113 /*
114 * See if we can re-use the old CE directly?
115 * That way we get the uptodate stat info.
116 */
117 if (path_matches(result, old) && same(result, old))
118 *result = *old;
43f91266 119 ce = result;
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120 ce->ce_flags &= ~htons(CE_STAGEMASK);
121 src += 2;
122 nr -= 2;
123 active_nr -= 2;
124 }
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125 *dst++ = ce;
126 src++;
127 nr--;
128 }
129}
130
131static void merge_stat_info(struct cache_entry **src, int nr)
132{
133 static struct cache_entry null_entry;
134 struct cache_entry **dst = src;
135 struct cache_entry *old = &null_entry;
136
137 while (nr) {
138 struct cache_entry *ce;
139
140 ce = src[0];
141
142 /* We throw away original cache entries except for the stat information */
143 if (!ce_stage(ce)) {
144 old = ce;
145 src++;
146 nr--;
147 active_nr--;
148 continue;
149 }
150 if (path_matches(ce, old) && same(ce, old))
151 *ce = *old;
152 ce->ce_flags &= ~htons(CE_STAGEMASK);
153 *dst++ = ce;
d99082e0 154 src++;
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155 nr--;
156 }
157}
158
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159static char *read_tree_usage = "read-tree (<sha> | -m <sha1> [<sha2> <sha3>])";
160
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161int main(int argc, char **argv)
162{
ca016f0e 163 int i, newfd, merge;
e83c5163 164 unsigned char sha1[20];
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165 static char lockfile[MAXPATHLEN+1];
166 const char *indexfile = get_index_file();
e83c5163 167
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168 snprintf(lockfile, sizeof(lockfile), "%s.lock", indexfile);
169
170 newfd = open(lockfile, O_RDWR | O_CREAT | O_EXCL, 0600);
83adac3c 171 if (newfd < 0)
2de381f9 172 die("unable to create new cachefile");
9614b8dc 173 atexit(remove_lock_file);
bb233d69 174 lockfile_name = lockfile;
83adac3c 175
ca016f0e 176 merge = 0;
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177 for (i = 1; i < argc; i++) {
178 const char *arg = argv[i];
179
d99082e0 180 /* "-m" stands for "merge", meaning we start in stage 1 */
83adac3c 181 if (!strcmp(arg, "-m")) {
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182 int i;
183 if (stage)
c5bac17a 184 die("-m needs to come first");
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185 read_cache();
186 for (i = 0; i < active_nr; i++) {
187 if (ce_stage(active_cache[i]))
c5bac17a 188 die("you need to resolve your current index first");
ca016f0e 189 }
d99082e0 190 stage = 1;
ca016f0e 191 merge = 1;
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192 continue;
193 }
9614b8dc 194 if (get_sha1_hex(arg, sha1) < 0)
c5bac17a 195 usage(read_tree_usage);
d99082e0 196 if (stage > 3)
c5bac17a 197 usage(read_tree_usage);
94537c78 198 if (unpack_tree(sha1) < 0)
2de381f9 199 die("failed to unpack tree object %s", arg);
d99082e0 200 stage++;
83adac3c 201 }
ca016f0e 202 if (merge) {
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203 switch (stage) {
204 case 4: /* Three-way merge */
205 trivially_merge_cache(active_cache, active_nr);
206 break;
207 case 2: /* Just read a tree, merge with old cache contents */
208 merge_stat_info(active_cache, active_nr);
209 break;
210 default:
211 die("just how do you expect me to merge %d trees?", stage-1);
212 }
ca016f0e 213 }
bb233d69 214 if (write_cache(newfd, active_cache, active_nr) || rename(lockfile, indexfile))
2de381f9 215 die("unable to write new index file");
bb233d69 216 lockfile_name = NULL;
9614b8dc 217 return 0;
e83c5163 218}