Examples of resetting.
[git/git.git] / refs.c
CommitLineData
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1#include "refs.h"
2#include "cache.h"
3
4#include <errno.h>
5
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LT
6/* We allow "recursive" symbolic refs. Only within reason, though */
7#define MAXDEPTH 5
8
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9#ifndef USE_SYMLINK_HEAD
10#define USE_SYMLINK_HEAD 1
11#endif
12
a876ed83 13const char *resolve_ref(const char *path, unsigned char *sha1, int reading)
8a65ff76 14{
a876ed83
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15 int depth = MAXDEPTH, len;
16 char buffer[256];
ca8db142 17
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18 for (;;) {
19 struct stat st;
20 char *buf;
21 int fd;
8a65ff76 22
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23 if (--depth < 0)
24 return NULL;
ca8db142 25
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26 /* Special case: non-existing file.
27 * Not having the refs/heads/new-branch is OK
28 * if we are writing into it, so is .git/HEAD
29 * that points at refs/heads/master still to be
30 * born. It is NOT OK if we are resolving for
31 * reading.
32 */
33 if (lstat(path, &st) < 0) {
34 if (reading || errno != ENOENT)
35 return NULL;
36 memset(sha1, 0, 20);
37 return path;
38 }
ca8db142 39
a876ed83
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40 /* Follow "normalized" - ie "refs/.." symlinks by hand */
41 if (S_ISLNK(st.st_mode)) {
42 len = readlink(path, buffer, sizeof(buffer)-1);
43 if (len >= 5 && !memcmp("refs/", buffer, 5)) {
44 path = git_path("%.*s", len, buffer);
45 continue;
46 }
ca8db142 47 }
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48
49 /*
50 * Anything else, just open it and try to use it as
51 * a ref
52 */
53 fd = open(path, O_RDONLY);
54 if (fd < 0)
55 return NULL;
56 len = read(fd, buffer, sizeof(buffer)-1);
57 close(fd);
58
59 /*
60 * Is it a symbolic ref?
61 */
62 if (len < 4 || memcmp("ref:", buffer, 4))
63 break;
64 buf = buffer + 4;
65 len -= 4;
66 while (len && isspace(*buf))
67 buf++, len--;
68 while (len && isspace(buf[len-1]))
69 buf[--len] = 0;
70 path = git_path("%.*s", len, buf);
8a65ff76 71 }
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72 if (len < 40 || get_sha1_hex(buffer, sha1))
73 return NULL;
74 return path;
75}
76
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77int create_symref(const char *git_HEAD, const char *refs_heads_master)
78{
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79 const char *lockpath;
80 char ref[1000];
81 int fd, len, written;
82
303958dc 83#if USE_SYMLINK_HEAD
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84 if (!only_use_symrefs) {
85 unlink(git_HEAD);
86 if (!symlink(refs_heads_master, git_HEAD))
87 return 0;
88 fprintf(stderr, "no symlink - falling back to symbolic ref\n");
89 }
303958dc
JS
90#endif
91
8098a178
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92 len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
93 if (sizeof(ref) <= len) {
94 error("refname too long: %s", refs_heads_master);
95 return -1;
96 }
97 lockpath = mkpath("%s.lock", git_HEAD);
98 fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666);
99 written = write(fd, ref, len);
100 close(fd);
101 if (written != len) {
102 unlink(lockpath);
103 error("Unable to write to %s", lockpath);
104 return -2;
105 }
106 if (rename(lockpath, git_HEAD) < 0) {
107 unlink(lockpath);
108 error("Unable to create %s", git_HEAD);
109 return -3;
110 }
111 return 0;
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112}
113
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114int read_ref(const char *filename, unsigned char *sha1)
115{
116 if (resolve_ref(filename, sha1, 1))
117 return 0;
118 return -1;
8a65ff76
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119}
120
944d8589 121static int do_for_each_ref(const char *base, int (*fn)(const char *path, const unsigned char *sha1))
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122{
123 int retval = 0;
4ec99bf0 124 DIR *dir = opendir(git_path("%s", base));
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LT
125
126 if (dir) {
127 struct dirent *de;
128 int baselen = strlen(base);
129 char *path = xmalloc(baselen + 257);
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LT
130
131 if (!strncmp(base, "./", 2)) {
132 base += 2;
133 baselen -= 2;
134 }
8a65ff76 135 memcpy(path, base, baselen);
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LT
136 if (baselen && base[baselen-1] != '/')
137 path[baselen++] = '/';
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LT
138
139 while ((de = readdir(dir)) != NULL) {
140 unsigned char sha1[20];
141 struct stat st;
142 int namelen;
143
144 if (de->d_name[0] == '.')
145 continue;
146 namelen = strlen(de->d_name);
147 if (namelen > 255)
148 continue;
149 memcpy(path + baselen, de->d_name, namelen+1);
a7e66ae3 150 if (stat(git_path("%s", path), &st) < 0)
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LT
151 continue;
152 if (S_ISDIR(st.st_mode)) {
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LT
153 retval = do_for_each_ref(path, fn);
154 if (retval)
155 break;
156 continue;
157 }
ca8db142 158 if (read_ref(git_path("%s", path), sha1) < 0)
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LT
159 continue;
160 if (!has_sha1_file(sha1))
161 continue;
162 retval = fn(path, sha1);
163 if (retval)
164 break;
165 }
166 free(path);
167 closedir(dir);
168 }
169 return retval;
170}
171
723c31fe
LT
172int head_ref(int (*fn)(const char *path, const unsigned char *sha1))
173{
174 unsigned char sha1[20];
ca8db142 175 if (!read_ref(git_path("HEAD"), sha1))
99a0a6e0 176 return fn("HEAD", sha1);
2f34ba32 177 return 0;
723c31fe
LT
178}
179
944d8589 180int for_each_ref(int (*fn)(const char *path, const unsigned char *sha1))
8a65ff76 181{
99a0a6e0 182 return do_for_each_ref("refs", fn);
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LT
183}
184
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DB
185static char *ref_file_name(const char *ref)
186{
187 char *base = get_refs_directory();
188 int baselen = strlen(base);
189 int reflen = strlen(ref);
190 char *ret = xmalloc(baselen + 2 + reflen);
191 sprintf(ret, "%s/%s", base, ref);
192 return ret;
193}
194
195static char *ref_lock_file_name(const char *ref)
196{
197 char *base = get_refs_directory();
198 int baselen = strlen(base);
199 int reflen = strlen(ref);
200 char *ret = xmalloc(baselen + 7 + reflen);
201 sprintf(ret, "%s/%s.lock", base, ref);
202 return ret;
203}
204
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205int get_ref_sha1(const char *ref, unsigned char *sha1)
206{
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207 const char *filename;
208
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209 if (check_ref_format(ref))
210 return -1;
ca8db142
LT
211 filename = git_path("refs/%s", ref);
212 return read_ref(filename, sha1);
95fc7512
DB
213}
214
215static int lock_ref_file(const char *filename, const char *lock_filename,
216 const unsigned char *old_sha1)
217{
218 int fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
219 unsigned char current_sha1[20];
220 int retval;
221 if (fd < 0) {
222 return error("Couldn't open lock file for %s: %s",
223 filename, strerror(errno));
224 }
ca8db142 225 retval = read_ref(filename, current_sha1);
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DB
226 if (old_sha1) {
227 if (retval) {
228 close(fd);
229 unlink(lock_filename);
230 return error("Could not read the current value of %s",
231 filename);
232 }
233 if (memcmp(current_sha1, old_sha1, 20)) {
234 close(fd);
235 unlink(lock_filename);
236 error("The current value of %s is %s",
237 filename, sha1_to_hex(current_sha1));
238 return error("Expected %s",
239 sha1_to_hex(old_sha1));
240 }
241 } else {
242 if (!retval) {
243 close(fd);
244 unlink(lock_filename);
245 return error("Unexpectedly found a value of %s for %s",
246 sha1_to_hex(current_sha1), filename);
247 }
248 }
249 return fd;
250}
251
252int lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
253{
254 char *filename;
255 char *lock_filename;
256 int retval;
257 if (check_ref_format(ref))
258 return -1;
259 filename = ref_file_name(ref);
260 lock_filename = ref_lock_file_name(ref);
261 retval = lock_ref_file(filename, lock_filename, old_sha1);
262 free(filename);
263 free(lock_filename);
264 return retval;
265}
266
267static int write_ref_file(const char *filename,
268 const char *lock_filename, int fd,
269 const unsigned char *sha1)
270{
271 char *hex = sha1_to_hex(sha1);
272 char term = '\n';
273 if (write(fd, hex, 40) < 40 ||
274 write(fd, &term, 1) < 1) {
275 error("Couldn't write %s\n", filename);
276 close(fd);
277 return -1;
278 }
279 close(fd);
280 rename(lock_filename, filename);
281 return 0;
282}
283
284int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1)
285{
286 char *filename;
287 char *lock_filename;
288 int retval;
289 if (fd < 0)
290 return -1;
291 if (check_ref_format(ref))
292 return -1;
293 filename = ref_file_name(ref);
294 lock_filename = ref_lock_file_name(ref);
64224caf
JH
295 if (safe_create_leading_directories(filename))
296 die("unable to create leading directory for %s", filename);
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DB
297 retval = write_ref_file(filename, lock_filename, fd, sha1);
298 free(filename);
299 free(lock_filename);
300 return retval;
301}
302
03feddd6
JH
303/*
304 * Make sure "ref" is something reasonable to have under ".git/refs/";
305 * We do not like it if:
306 *
307 * - any path component of it begins with ".", or
308 * - it has double dots "..", or
309 * - it has ASCII control character, "~", "^", ":" or SP, anywhere, or
310 * - it ends with a "/".
311 */
312
313static inline int bad_ref_char(int ch)
314{
315 return (((unsigned) ch) <= ' ' ||
316 ch == '~' || ch == '^' || ch == ':');
317}
318
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319int check_ref_format(const char *ref)
320{
03feddd6
JH
321 int ch, level;
322 const char *cp = ref;
323
324 level = 0;
325 while (1) {
326 while ((ch = *cp++) == '/')
327 ; /* tolerate duplicated slashes */
328 if (!ch)
329 return -1; /* should not end with slashes */
330
331 /* we are at the beginning of the path component */
332 if (ch == '.' || bad_ref_char(ch))
333 return -1;
334
335 /* scan the rest of the path component */
336 while ((ch = *cp++) != 0) {
337 if (bad_ref_char(ch))
338 return -1;
339 if (ch == '/')
340 break;
341 if (ch == '.' && *cp == '.')
342 return -1;
343 }
344 level++;
345 if (!ch) {
346 if (level < 2)
347 return -1; /* at least of form "heads/blah" */
ee34518d 348
06bf6ac4
JH
349 /* Do not allow ref name to end in "HEAD"
350 * Note that cp is poiting at one past NUL at the end.
351 * i.e. cp[-1] = NUL.
352 */
353 if (5 <= cp - ref && !strcmp(cp - 5, "HEAD"))
ee34518d
JS
354 return -1;
355
03feddd6
JH
356 return 0;
357 }
358 }
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DB
359}
360
361int write_ref_sha1_unlocked(const char *ref, const unsigned char *sha1)
362{
363 char *filename;
364 char *lock_filename;
365 int fd;
366 int retval;
367 if (check_ref_format(ref))
368 return -1;
369 filename = ref_file_name(ref);
370 lock_filename = ref_lock_file_name(ref);
64224caf
JH
371 if (safe_create_leading_directories(filename))
372 die("unable to create leading directory for %s", filename);
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373 fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
374 if (fd < 0) {
375 error("Writing %s", lock_filename);
376 perror("Open");
377 }
378 retval = write_ref_file(filename, lock_filename, fd, sha1);
379 free(filename);
380 free(lock_filename);
381 return retval;
382}