Allow git-merge not to commit.
[git.git] / refs.c
1 #include "refs.h"
2 #include "cache.h"
3
4 #include <errno.h>
5
6 /* We allow "recursive" symbolic refs. Only within reason, though */
7 #define MAXDEPTH 5
8
9 #ifndef USE_SYMLINK_HEAD
10 #define USE_SYMLINK_HEAD 1
11 #endif
12
13 int validate_symref(const char *path)
14 {
15         struct stat st;
16         char *buf, buffer[256];
17         int len, fd;
18
19         if (lstat(path, &st) < 0)
20                 return -1;
21
22         /* Make sure it is a "refs/.." symlink */
23         if (S_ISLNK(st.st_mode)) {
24                 len = readlink(path, buffer, sizeof(buffer)-1);
25                 if (len >= 5 && !memcmp("refs/", buffer, 5))
26                         return 0;
27                 return -1;
28         }
29
30         /*
31          * Anything else, just open it and try to see if it is a symbolic ref.
32          */
33         fd = open(path, O_RDONLY);
34         if (fd < 0)
35                 return -1;
36         len = read(fd, buffer, sizeof(buffer)-1);
37         close(fd);
38
39         /*
40          * Is it a symbolic ref?
41          */
42         if (len < 4 || memcmp("ref:", buffer, 4))
43                 return -1;
44         buf = buffer + 4;
45         len -= 4;
46         while (len && isspace(*buf))
47                 buf++, len--;
48         if (len >= 5 && !memcmp("refs/", buf, 5))
49                 return 0;
50         return -1;
51 }
52
53 const char *resolve_ref(const char *path, unsigned char *sha1, int reading)
54 {
55         int depth = MAXDEPTH, len;
56         char buffer[256];
57
58         for (;;) {
59                 struct stat st;
60                 char *buf;
61                 int fd;
62
63                 if (--depth < 0)
64                         return NULL;
65
66                 /* Special case: non-existing file.
67                  * Not having the refs/heads/new-branch is OK
68                  * if we are writing into it, so is .git/HEAD
69                  * that points at refs/heads/master still to be
70                  * born.  It is NOT OK if we are resolving for
71                  * reading.
72                  */
73                 if (lstat(path, &st) < 0) {
74                         if (reading || errno != ENOENT)
75                                 return NULL;
76                         memset(sha1, 0, 20);
77                         return path;
78                 }
79
80                 /* Follow "normalized" - ie "refs/.." symlinks by hand */
81                 if (S_ISLNK(st.st_mode)) {
82                         len = readlink(path, buffer, sizeof(buffer)-1);
83                         if (len >= 5 && !memcmp("refs/", buffer, 5)) {
84                                 path = git_path("%.*s", len, buffer);
85                                 continue;
86                         }
87                 }
88
89                 /*
90                  * Anything else, just open it and try to use it as
91                  * a ref
92                  */
93                 fd = open(path, O_RDONLY);
94                 if (fd < 0)
95                         return NULL;
96                 len = read(fd, buffer, sizeof(buffer)-1);
97                 close(fd);
98
99                 /*
100                  * Is it a symbolic ref?
101                  */
102                 if (len < 4 || memcmp("ref:", buffer, 4))
103                         break;
104                 buf = buffer + 4;
105                 len -= 4;
106                 while (len && isspace(*buf))
107                         buf++, len--;
108                 while (len && isspace(buf[len-1]))
109                         buf[--len] = 0;
110                 path = git_path("%.*s", len, buf);
111         }
112         if (len < 40 || get_sha1_hex(buffer, sha1))
113                 return NULL;
114         return path;
115 }
116
117 int create_symref(const char *git_HEAD, const char *refs_heads_master)
118 {
119 #if USE_SYMLINK_HEAD
120         unlink(git_HEAD);
121         return symlink(refs_heads_master, git_HEAD);
122 #else
123         const char *lockpath;
124         char ref[1000];
125         int fd, len, written;
126
127         len = snprintf(ref, sizeof(ref), "ref: %s\n", refs_heads_master);
128         if (sizeof(ref) <= len) {
129                 error("refname too long: %s", refs_heads_master);
130                 return -1;
131         }
132         lockpath = mkpath("%s.lock", git_HEAD);
133         fd = open(lockpath, O_CREAT | O_EXCL | O_WRONLY, 0666); 
134         written = write(fd, ref, len);
135         close(fd);
136         if (written != len) {
137                 unlink(lockpath);
138                 error("Unable to write to %s", lockpath);
139                 return -2;
140         }
141         if (rename(lockpath, git_HEAD) < 0) {
142                 unlink(lockpath);
143                 error("Unable to create %s", git_HEAD);
144                 return -3;
145         }
146         return 0;
147 #endif
148 }
149
150 int read_ref(const char *filename, unsigned char *sha1)
151 {
152         if (resolve_ref(filename, sha1, 1))
153                 return 0;
154         return -1;
155 }
156
157 static int do_for_each_ref(const char *base, int (*fn)(const char *path, const unsigned char *sha1))
158 {
159         int retval = 0;
160         DIR *dir = opendir(git_path("%s", base));
161
162         if (dir) {
163                 struct dirent *de;
164                 int baselen = strlen(base);
165                 char *path = xmalloc(baselen + 257);
166
167                 if (!strncmp(base, "./", 2)) {
168                         base += 2;
169                         baselen -= 2;
170                 }
171                 memcpy(path, base, baselen);
172                 if (baselen && base[baselen-1] != '/')
173                         path[baselen++] = '/';
174
175                 while ((de = readdir(dir)) != NULL) {
176                         unsigned char sha1[20];
177                         struct stat st;
178                         int namelen;
179
180                         if (de->d_name[0] == '.')
181                                 continue;
182                         namelen = strlen(de->d_name);
183                         if (namelen > 255)
184                                 continue;
185                         memcpy(path + baselen, de->d_name, namelen+1);
186                         if (stat(git_path("%s", path), &st) < 0)
187                                 continue;
188                         if (S_ISDIR(st.st_mode)) {
189                                 retval = do_for_each_ref(path, fn);
190                                 if (retval)
191                                         break;
192                                 continue;
193                         }
194                         if (read_ref(git_path("%s", path), sha1) < 0)
195                                 continue;
196                         if (!has_sha1_file(sha1))
197                                 continue;
198                         retval = fn(path, sha1);
199                         if (retval)
200                                 break;
201                 }
202                 free(path);
203                 closedir(dir);
204         }
205         return retval;
206 }
207
208 int head_ref(int (*fn)(const char *path, const unsigned char *sha1))
209 {
210         unsigned char sha1[20];
211         if (!read_ref(git_path("HEAD"), sha1))
212                 return fn("HEAD", sha1);
213         return 0;
214 }
215
216 int for_each_ref(int (*fn)(const char *path, const unsigned char *sha1))
217 {
218         return do_for_each_ref("refs", fn);
219 }
220
221 static char *ref_file_name(const char *ref)
222 {
223         char *base = get_refs_directory();
224         int baselen = strlen(base);
225         int reflen = strlen(ref);
226         char *ret = xmalloc(baselen + 2 + reflen);
227         sprintf(ret, "%s/%s", base, ref);
228         return ret;
229 }
230
231 static char *ref_lock_file_name(const char *ref)
232 {
233         char *base = get_refs_directory();
234         int baselen = strlen(base);
235         int reflen = strlen(ref);
236         char *ret = xmalloc(baselen + 7 + reflen);
237         sprintf(ret, "%s/%s.lock", base, ref);
238         return ret;
239 }
240
241 int get_ref_sha1(const char *ref, unsigned char *sha1)
242 {
243         const char *filename;
244
245         if (check_ref_format(ref))
246                 return -1;
247         filename = git_path("refs/%s", ref);
248         return read_ref(filename, sha1);
249 }
250
251 static int lock_ref_file(const char *filename, const char *lock_filename,
252                          const unsigned char *old_sha1)
253 {
254         int fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
255         unsigned char current_sha1[20];
256         int retval;
257         if (fd < 0) {
258                 return error("Couldn't open lock file for %s: %s",
259                              filename, strerror(errno));
260         }
261         retval = read_ref(filename, current_sha1);
262         if (old_sha1) {
263                 if (retval) {
264                         close(fd);
265                         unlink(lock_filename);
266                         return error("Could not read the current value of %s",
267                                      filename);
268                 }
269                 if (memcmp(current_sha1, old_sha1, 20)) {
270                         close(fd);
271                         unlink(lock_filename);
272                         error("The current value of %s is %s",
273                               filename, sha1_to_hex(current_sha1));
274                         return error("Expected %s",
275                                      sha1_to_hex(old_sha1));
276                 }
277         } else {
278                 if (!retval) {
279                         close(fd);
280                         unlink(lock_filename);
281                         return error("Unexpectedly found a value of %s for %s",
282                                      sha1_to_hex(current_sha1), filename);
283                 }
284         }
285         return fd;
286 }
287
288 int lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
289 {
290         char *filename;
291         char *lock_filename;
292         int retval;
293         if (check_ref_format(ref))
294                 return -1;
295         filename = ref_file_name(ref);
296         lock_filename = ref_lock_file_name(ref);
297         retval = lock_ref_file(filename, lock_filename, old_sha1);
298         free(filename);
299         free(lock_filename);
300         return retval;
301 }
302
303 static int write_ref_file(const char *filename,
304                           const char *lock_filename, int fd,
305                           const unsigned char *sha1)
306 {
307         char *hex = sha1_to_hex(sha1);
308         char term = '\n';
309         if (write(fd, hex, 40) < 40 ||
310             write(fd, &term, 1) < 1) {
311                 error("Couldn't write %s\n", filename);
312                 close(fd);
313                 return -1;
314         }
315         close(fd);
316         rename(lock_filename, filename);
317         return 0;
318 }
319
320 int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1)
321 {
322         char *filename;
323         char *lock_filename;
324         int retval;
325         if (fd < 0)
326                 return -1;
327         if (check_ref_format(ref))
328                 return -1;
329         filename = ref_file_name(ref);
330         lock_filename = ref_lock_file_name(ref);
331         retval = write_ref_file(filename, lock_filename, fd, sha1);
332         free(filename);
333         free(lock_filename);
334         return retval;
335 }
336
337 /*
338  * Make sure "ref" is something reasonable to have under ".git/refs/";
339  * We do not like it if:
340  *
341  * - any path component of it begins with ".", or
342  * - it has double dots "..", or
343  * - it has ASCII control character, "~", "^", ":" or SP, anywhere, or
344  * - it ends with a "/".
345  */
346
347 static inline int bad_ref_char(int ch)
348 {
349         return (((unsigned) ch) <= ' ' ||
350                 ch == '~' || ch == '^' || ch == ':');
351 }
352
353 int check_ref_format(const char *ref)
354 {
355         int ch, level;
356         const char *cp = ref;
357
358         level = 0;
359         while (1) {
360                 while ((ch = *cp++) == '/')
361                         ; /* tolerate duplicated slashes */
362                 if (!ch)
363                         return -1; /* should not end with slashes */
364
365                 /* we are at the beginning of the path component */
366                 if (ch == '.' || bad_ref_char(ch))
367                         return -1;
368
369                 /* scan the rest of the path component */
370                 while ((ch = *cp++) != 0) {
371                         if (bad_ref_char(ch))
372                                 return -1;
373                         if (ch == '/')
374                                 break;
375                         if (ch == '.' && *cp == '.')
376                                 return -1;
377                 }
378                 level++;
379                 if (!ch) {
380                         if (level < 2)
381                                 return -1; /* at least of form "heads/blah" */
382                         return 0;
383                 }
384         }
385 }
386
387 int write_ref_sha1_unlocked(const char *ref, const unsigned char *sha1)
388 {
389         char *filename;
390         char *lock_filename;
391         int fd;
392         int retval;
393         if (check_ref_format(ref))
394                 return -1;
395         filename = ref_file_name(ref);
396         lock_filename = ref_lock_file_name(ref);
397         fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
398         if (fd < 0) {
399                 error("Writing %s", lock_filename);
400                 perror("Open");
401         }
402         retval = write_ref_file(filename, lock_filename, fd, sha1);
403         free(filename);
404         free(lock_filename);
405         return retval;
406 }