receive-pack: detect aliased updates which can occur with symrefs
[git] / ll-merge.c
1 /*
2  * Low level 3-way in-core file merge.
3  *
4  * Copyright (c) 2007 Junio C Hamano
5  */
6
7 #include "cache.h"
8 #include "attr.h"
9 #include "xdiff-interface.h"
10 #include "run-command.h"
11 #include "ll-merge.h"
12
13 struct ll_merge_driver;
14
15 typedef int (*ll_merge_fn)(const struct ll_merge_driver *,
16                            mmbuffer_t *result,
17                            const char *path,
18                            mmfile_t *orig,
19                            mmfile_t *src1, const char *name1,
20                            mmfile_t *src2, const char *name2,
21                            int flag,
22                            int marker_size);
23
24 struct ll_merge_driver {
25         const char *name;
26         const char *description;
27         ll_merge_fn fn;
28         const char *recursive;
29         struct ll_merge_driver *next;
30         char *cmdline;
31 };
32
33 /*
34  * Built-in low-levels
35  */
36 static int ll_binary_merge(const struct ll_merge_driver *drv_unused,
37                            mmbuffer_t *result,
38                            const char *path_unused,
39                            mmfile_t *orig,
40                            mmfile_t *src1, const char *name1,
41                            mmfile_t *src2, const char *name2,
42                            int flag, int marker_size)
43 {
44         /*
45          * The tentative merge result is "ours" for the final round,
46          * or common ancestor for an internal merge.  Still return
47          * "conflicted merge" status.
48          */
49         mmfile_t *stolen = (flag & 01) ? orig : src1;
50
51         result->ptr = stolen->ptr;
52         result->size = stolen->size;
53         stolen->ptr = NULL;
54         return 1;
55 }
56
57 static int ll_xdl_merge(const struct ll_merge_driver *drv_unused,
58                         mmbuffer_t *result,
59                         const char *path,
60                         mmfile_t *orig,
61                         mmfile_t *src1, const char *name1,
62                         mmfile_t *src2, const char *name2,
63                         int flag, int marker_size)
64 {
65         xmparam_t xmp;
66         int style = 0;
67         int favor = (flag >> 1) & 03;
68
69         if (buffer_is_binary(orig->ptr, orig->size) ||
70             buffer_is_binary(src1->ptr, src1->size) ||
71             buffer_is_binary(src2->ptr, src2->size)) {
72                 warning("Cannot merge binary files: %s (%s vs. %s)\n",
73                         path, name1, name2);
74                 return ll_binary_merge(drv_unused, result,
75                                        path,
76                                        orig, src1, name1,
77                                        src2, name2,
78                                        flag, marker_size);
79         }
80
81         memset(&xmp, 0, sizeof(xmp));
82         if (git_xmerge_style >= 0)
83                 style = git_xmerge_style;
84         if (marker_size > 0)
85                 xmp.marker_size = marker_size;
86         return xdl_merge(orig,
87                          src1, name1,
88                          src2, name2,
89                          &xmp, XDL_MERGE_FLAGS(XDL_MERGE_ZEALOUS, style, favor),
90                          result);
91 }
92
93 static int ll_union_merge(const struct ll_merge_driver *drv_unused,
94                           mmbuffer_t *result,
95                           const char *path_unused,
96                           mmfile_t *orig,
97                           mmfile_t *src1, const char *name1,
98                           mmfile_t *src2, const char *name2,
99                           int flag, int marker_size)
100 {
101         char *src, *dst;
102         long size;
103         int status, saved_style;
104
105         /* We have to force the RCS "merge" style */
106         saved_style = git_xmerge_style;
107         git_xmerge_style = 0;
108         status = ll_xdl_merge(drv_unused, result, path_unused,
109                               orig, src1, NULL, src2, NULL,
110                               flag, marker_size);
111         git_xmerge_style = saved_style;
112         if (status <= 0)
113                 return status;
114         size = result->size;
115         src = dst = result->ptr;
116         while (size) {
117                 char ch;
118                 if ((marker_size < size) &&
119                     (*src == '<' || *src == '=' || *src == '>')) {
120                         int i;
121                         ch = *src;
122                         for (i = 0; i < marker_size; i++)
123                                 if (src[i] != ch)
124                                         goto not_a_marker;
125                         if (src[marker_size] != '\n')
126                                 goto not_a_marker;
127                         src += marker_size + 1;
128                         size -= marker_size + 1;
129                         continue;
130                 }
131         not_a_marker:
132                 do {
133                         ch = *src++;
134                         *dst++ = ch;
135                         size--;
136                 } while (ch != '\n' && size);
137         }
138         result->size = dst - result->ptr;
139         return 0;
140 }
141
142 #define LL_BINARY_MERGE 0
143 #define LL_TEXT_MERGE 1
144 #define LL_UNION_MERGE 2
145 static struct ll_merge_driver ll_merge_drv[] = {
146         { "binary", "built-in binary merge", ll_binary_merge },
147         { "text", "built-in 3-way text merge", ll_xdl_merge },
148         { "union", "built-in union merge", ll_union_merge },
149 };
150
151 static void create_temp(mmfile_t *src, char *path)
152 {
153         int fd;
154
155         strcpy(path, ".merge_file_XXXXXX");
156         fd = xmkstemp(path);
157         if (write_in_full(fd, src->ptr, src->size) != src->size)
158                 die_errno("unable to write temp-file");
159         close(fd);
160 }
161
162 /*
163  * User defined low-level merge driver support.
164  */
165 static int ll_ext_merge(const struct ll_merge_driver *fn,
166                         mmbuffer_t *result,
167                         const char *path,
168                         mmfile_t *orig,
169                         mmfile_t *src1, const char *name1,
170                         mmfile_t *src2, const char *name2,
171                         int flag, int marker_size)
172 {
173         char temp[4][50];
174         struct strbuf cmd = STRBUF_INIT;
175         struct strbuf_expand_dict_entry dict[] = {
176                 { "O", temp[0] },
177                 { "A", temp[1] },
178                 { "B", temp[2] },
179                 { "L", temp[3] },
180                 { NULL }
181         };
182         const char *args[] = { NULL, NULL };
183         int status, fd, i;
184         struct stat st;
185
186         if (fn->cmdline == NULL)
187                 die("custom merge driver %s lacks command line.", fn->name);
188
189         result->ptr = NULL;
190         result->size = 0;
191         create_temp(orig, temp[0]);
192         create_temp(src1, temp[1]);
193         create_temp(src2, temp[2]);
194         sprintf(temp[3], "%d", marker_size);
195
196         strbuf_expand(&cmd, fn->cmdline, strbuf_expand_dict_cb, &dict);
197
198         args[0] = cmd.buf;
199         status = run_command_v_opt(args, RUN_USING_SHELL);
200         fd = open(temp[1], O_RDONLY);
201         if (fd < 0)
202                 goto bad;
203         if (fstat(fd, &st))
204                 goto close_bad;
205         result->size = st.st_size;
206         result->ptr = xmalloc(result->size + 1);
207         if (read_in_full(fd, result->ptr, result->size) != result->size) {
208                 free(result->ptr);
209                 result->ptr = NULL;
210                 result->size = 0;
211         }
212  close_bad:
213         close(fd);
214  bad:
215         for (i = 0; i < 3; i++)
216                 unlink_or_warn(temp[i]);
217         strbuf_release(&cmd);
218         return status;
219 }
220
221 /*
222  * merge.default and merge.driver configuration items
223  */
224 static struct ll_merge_driver *ll_user_merge, **ll_user_merge_tail;
225 static const char *default_ll_merge;
226
227 static int read_merge_config(const char *var, const char *value, void *cb)
228 {
229         struct ll_merge_driver *fn;
230         const char *ep, *name;
231         int namelen;
232
233         if (!strcmp(var, "merge.default")) {
234                 if (value)
235                         default_ll_merge = xstrdup(value);
236                 return 0;
237         }
238
239         /*
240          * We are not interested in anything but "merge.<name>.variable";
241          * especially, we do not want to look at variables such as
242          * "merge.summary", "merge.tool", and "merge.verbosity".
243          */
244         if (prefixcmp(var, "merge.") || (ep = strrchr(var, '.')) == var + 5)
245                 return 0;
246
247         /*
248          * Find existing one as we might be processing merge.<name>.var2
249          * after seeing merge.<name>.var1.
250          */
251         name = var + 6;
252         namelen = ep - name;
253         for (fn = ll_user_merge; fn; fn = fn->next)
254                 if (!strncmp(fn->name, name, namelen) && !fn->name[namelen])
255                         break;
256         if (!fn) {
257                 fn = xcalloc(1, sizeof(struct ll_merge_driver));
258                 fn->name = xmemdupz(name, namelen);
259                 fn->fn = ll_ext_merge;
260                 *ll_user_merge_tail = fn;
261                 ll_user_merge_tail = &(fn->next);
262         }
263
264         ep++;
265
266         if (!strcmp("name", ep)) {
267                 if (!value)
268                         return error("%s: lacks value", var);
269                 fn->description = xstrdup(value);
270                 return 0;
271         }
272
273         if (!strcmp("driver", ep)) {
274                 if (!value)
275                         return error("%s: lacks value", var);
276                 /*
277                  * merge.<name>.driver specifies the command line:
278                  *
279                  *      command-line
280                  *
281                  * The command-line will be interpolated with the following
282                  * tokens and is given to the shell:
283                  *
284                  *    %O - temporary file name for the merge base.
285                  *    %A - temporary file name for our version.
286                  *    %B - temporary file name for the other branches' version.
287                  *    %L - conflict marker length
288                  *
289                  * The external merge driver should write the results in the
290                  * file named by %A, and signal that it has done with zero exit
291                  * status.
292                  */
293                 fn->cmdline = xstrdup(value);
294                 return 0;
295         }
296
297         if (!strcmp("recursive", ep)) {
298                 if (!value)
299                         return error("%s: lacks value", var);
300                 fn->recursive = xstrdup(value);
301                 return 0;
302         }
303
304         return 0;
305 }
306
307 static void initialize_ll_merge(void)
308 {
309         if (ll_user_merge_tail)
310                 return;
311         ll_user_merge_tail = &ll_user_merge;
312         git_config(read_merge_config, NULL);
313 }
314
315 static const struct ll_merge_driver *find_ll_merge_driver(const char *merge_attr)
316 {
317         struct ll_merge_driver *fn;
318         const char *name;
319         int i;
320
321         initialize_ll_merge();
322
323         if (ATTR_TRUE(merge_attr))
324                 return &ll_merge_drv[LL_TEXT_MERGE];
325         else if (ATTR_FALSE(merge_attr))
326                 return &ll_merge_drv[LL_BINARY_MERGE];
327         else if (ATTR_UNSET(merge_attr)) {
328                 if (!default_ll_merge)
329                         return &ll_merge_drv[LL_TEXT_MERGE];
330                 else
331                         name = default_ll_merge;
332         }
333         else
334                 name = merge_attr;
335
336         for (fn = ll_user_merge; fn; fn = fn->next)
337                 if (!strcmp(fn->name, name))
338                         return fn;
339
340         for (i = 0; i < ARRAY_SIZE(ll_merge_drv); i++)
341                 if (!strcmp(ll_merge_drv[i].name, name))
342                         return &ll_merge_drv[i];
343
344         /* default to the 3-way */
345         return &ll_merge_drv[LL_TEXT_MERGE];
346 }
347
348 static int git_path_check_merge(const char *path, struct git_attr_check check[2])
349 {
350         if (!check[0].attr) {
351                 check[0].attr = git_attr("merge");
352                 check[1].attr = git_attr("conflict-marker-size");
353         }
354         return git_checkattr(path, 2, check);
355 }
356
357 int ll_merge(mmbuffer_t *result_buf,
358              const char *path,
359              mmfile_t *ancestor,
360              mmfile_t *ours, const char *our_label,
361              mmfile_t *theirs, const char *their_label,
362              int flag)
363 {
364         static struct git_attr_check check[2];
365         const char *ll_driver_name = NULL;
366         int marker_size = DEFAULT_CONFLICT_MARKER_SIZE;
367         const struct ll_merge_driver *driver;
368         int virtual_ancestor = flag & 01;
369
370         if (!git_path_check_merge(path, check)) {
371                 ll_driver_name = check[0].value;
372                 if (check[1].value) {
373                         marker_size = atoi(check[1].value);
374                         if (marker_size <= 0)
375                                 marker_size = DEFAULT_CONFLICT_MARKER_SIZE;
376                 }
377         }
378         driver = find_ll_merge_driver(ll_driver_name);
379         if (virtual_ancestor && driver->recursive)
380                 driver = find_ll_merge_driver(driver->recursive);
381         return driver->fn(driver, result_buf, path, ancestor,
382                           ours, our_label, theirs, their_label,
383                           flag, marker_size);
384 }
385
386 int ll_merge_marker_size(const char *path)
387 {
388         static struct git_attr_check check;
389         int marker_size = DEFAULT_CONFLICT_MARKER_SIZE;
390
391         if (!check.attr)
392                 check.attr = git_attr("conflict-marker-size");
393         if (!git_checkattr(path, 1, &check) && check.value) {
394                 marker_size = atoi(check.value);
395                 if (marker_size <= 0)
396                         marker_size = DEFAULT_CONFLICT_MARKER_SIZE;
397         }
398         return marker_size;
399 }