git svn: catch lack of upstream info for dcommit earlier
[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 "interpolate.h"
12 #include "ll-merge.h"
13
14 struct ll_merge_driver;
15
16 typedef int (*ll_merge_fn)(const struct ll_merge_driver *,
17                            mmbuffer_t *result,
18                            const char *path,
19                            mmfile_t *orig,
20                            mmfile_t *src1, const char *name1,
21                            mmfile_t *src2, const char *name2,
22                            int virtual_ancestor);
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 virtual_ancestor)
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 = virtual_ancestor ? 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_unused,
60                         mmfile_t *orig,
61                         mmfile_t *src1, const char *name1,
62                         mmfile_t *src2, const char *name2,
63                         int virtual_ancestor)
64 {
65         xpparam_t xpp;
66
67         if (buffer_is_binary(orig->ptr, orig->size) ||
68             buffer_is_binary(src1->ptr, src1->size) ||
69             buffer_is_binary(src2->ptr, src2->size)) {
70                 warning("Cannot merge binary files: %s vs. %s\n",
71                         name1, name2);
72                 return ll_binary_merge(drv_unused, result,
73                                        path_unused,
74                                        orig, src1, name1,
75                                        src2, name2,
76                                        virtual_ancestor);
77         }
78
79         memset(&xpp, 0, sizeof(xpp));
80         return xdl_merge(orig,
81                          src1, name1,
82                          src2, name2,
83                          &xpp, XDL_MERGE_ZEALOUS,
84                          result);
85 }
86
87 static int ll_union_merge(const struct ll_merge_driver *drv_unused,
88                           mmbuffer_t *result,
89                           const char *path_unused,
90                           mmfile_t *orig,
91                           mmfile_t *src1, const char *name1,
92                           mmfile_t *src2, const char *name2,
93                           int virtual_ancestor)
94 {
95         char *src, *dst;
96         long size;
97         const int marker_size = 7;
98
99         int status = ll_xdl_merge(drv_unused, result, path_unused,
100                                   orig, src1, NULL, src2, NULL,
101                                   virtual_ancestor);
102         if (status <= 0)
103                 return status;
104         size = result->size;
105         src = dst = result->ptr;
106         while (size) {
107                 char ch;
108                 if ((marker_size < size) &&
109                     (*src == '<' || *src == '=' || *src == '>')) {
110                         int i;
111                         ch = *src;
112                         for (i = 0; i < marker_size; i++)
113                                 if (src[i] != ch)
114                                         goto not_a_marker;
115                         if (src[marker_size] != '\n')
116                                 goto not_a_marker;
117                         src += marker_size + 1;
118                         size -= marker_size + 1;
119                         continue;
120                 }
121         not_a_marker:
122                 do {
123                         ch = *src++;
124                         *dst++ = ch;
125                         size--;
126                 } while (ch != '\n' && size);
127         }
128         result->size = dst - result->ptr;
129         return 0;
130 }
131
132 #define LL_BINARY_MERGE 0
133 #define LL_TEXT_MERGE 1
134 #define LL_UNION_MERGE 2
135 static struct ll_merge_driver ll_merge_drv[] = {
136         { "binary", "built-in binary merge", ll_binary_merge },
137         { "text", "built-in 3-way text merge", ll_xdl_merge },
138         { "union", "built-in union merge", ll_union_merge },
139 };
140
141 static void create_temp(mmfile_t *src, char *path)
142 {
143         int fd;
144
145         strcpy(path, ".merge_file_XXXXXX");
146         fd = xmkstemp(path);
147         if (write_in_full(fd, src->ptr, src->size) != src->size)
148                 die("unable to write temp-file");
149         close(fd);
150 }
151
152 /*
153  * User defined low-level merge driver support.
154  */
155 static int ll_ext_merge(const struct ll_merge_driver *fn,
156                         mmbuffer_t *result,
157                         const char *path,
158                         mmfile_t *orig,
159                         mmfile_t *src1, const char *name1,
160                         mmfile_t *src2, const char *name2,
161                         int virtual_ancestor)
162 {
163         char temp[3][50];
164         char cmdbuf[2048];
165         struct interp table[] = {
166                 { "%O" },
167                 { "%A" },
168                 { "%B" },
169         };
170         struct child_process child;
171         const char *args[20];
172         int status, fd, i;
173         struct stat st;
174
175         if (fn->cmdline == NULL)
176                 die("custom merge driver %s lacks command line.", fn->name);
177
178         result->ptr = NULL;
179         result->size = 0;
180         create_temp(orig, temp[0]);
181         create_temp(src1, temp[1]);
182         create_temp(src2, temp[2]);
183
184         interp_set_entry(table, 0, temp[0]);
185         interp_set_entry(table, 1, temp[1]);
186         interp_set_entry(table, 2, temp[2]);
187
188         interpolate(cmdbuf, sizeof(cmdbuf), fn->cmdline, table, 3);
189
190         memset(&child, 0, sizeof(child));
191         child.argv = args;
192         args[0] = "sh";
193         args[1] = "-c";
194         args[2] = cmdbuf;
195         args[3] = NULL;
196
197         status = run_command(&child);
198         if (status < -ERR_RUN_COMMAND_FORK)
199                 ; /* failure in run-command */
200         else
201                 status = -status;
202         fd = open(temp[1], O_RDONLY);
203         if (fd < 0)
204                 goto bad;
205         if (fstat(fd, &st))
206                 goto close_bad;
207         result->size = st.st_size;
208         result->ptr = xmalloc(result->size + 1);
209         if (read_in_full(fd, result->ptr, result->size) != result->size) {
210                 free(result->ptr);
211                 result->ptr = NULL;
212                 result->size = 0;
213         }
214  close_bad:
215         close(fd);
216  bad:
217         for (i = 0; i < 3; i++)
218                 unlink(temp[i]);
219         return status;
220 }
221
222 /*
223  * merge.default and merge.driver configuration items
224  */
225 static struct ll_merge_driver *ll_user_merge, **ll_user_merge_tail;
226 static const char *default_ll_merge;
227
228 static int read_merge_config(const char *var, const char *value, void *cb)
229 {
230         struct ll_merge_driver *fn;
231         const char *ep, *name;
232         int namelen;
233
234         if (!strcmp(var, "merge.default")) {
235                 if (value)
236                         default_ll_merge = strdup(value);
237                 return 0;
238         }
239
240         /*
241          * We are not interested in anything but "merge.<name>.variable";
242          * especially, we do not want to look at variables such as
243          * "merge.summary", "merge.tool", and "merge.verbosity".
244          */
245         if (prefixcmp(var, "merge.") || (ep = strrchr(var, '.')) == var + 5)
246                 return 0;
247
248         /*
249          * Find existing one as we might be processing merge.<name>.var2
250          * after seeing merge.<name>.var1.
251          */
252         name = var + 6;
253         namelen = ep - name;
254         for (fn = ll_user_merge; fn; fn = fn->next)
255                 if (!strncmp(fn->name, name, namelen) && !fn->name[namelen])
256                         break;
257         if (!fn) {
258                 fn = xcalloc(1, sizeof(struct ll_merge_driver));
259                 fn->name = xmemdupz(name, namelen);
260                 fn->fn = ll_ext_merge;
261                 *ll_user_merge_tail = fn;
262                 ll_user_merge_tail = &(fn->next);
263         }
264
265         ep++;
266
267         if (!strcmp("name", ep)) {
268                 if (!value)
269                         return error("%s: lacks value", var);
270                 fn->description = strdup(value);
271                 return 0;
272         }
273
274         if (!strcmp("driver", ep)) {
275                 if (!value)
276                         return error("%s: lacks value", var);
277                 /*
278                  * merge.<name>.driver specifies the command line:
279                  *
280                  *      command-line
281                  *
282                  * The command-line will be interpolated with the following
283                  * tokens and is given to the shell:
284                  *
285                  *    %O - temporary file name for the merge base.
286                  *    %A - temporary file name for our version.
287                  *    %B - temporary file name for the other branches' version.
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 = strdup(value);
294                 return 0;
295         }
296
297         if (!strcmp("recursive", ep)) {
298                 if (!value)
299                         return error("%s: lacks value", var);
300                 fn->recursive = strdup(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 const char *git_path_check_merge(const char *path)
349 {
350         static struct git_attr_check attr_merge_check;
351
352         if (!attr_merge_check.attr)
353                 attr_merge_check.attr = git_attr("merge", 5);
354
355         if (git_checkattr(path, 1, &attr_merge_check))
356                 return NULL;
357         return attr_merge_check.value;
358 }
359
360 int ll_merge(mmbuffer_t *result_buf,
361              const char *path,
362              mmfile_t *ancestor,
363              mmfile_t *ours, const char *our_label,
364              mmfile_t *theirs, const char *their_label,
365              int virtual_ancestor)
366 {
367         const char *ll_driver_name;
368         const struct ll_merge_driver *driver;
369
370         ll_driver_name = git_path_check_merge(path);
371         driver = find_ll_merge_driver(ll_driver_name);
372
373         if (virtual_ancestor && driver->recursive)
374                 driver = find_ll_merge_driver(driver->recursive);
375         return driver->fn(driver, result_buf, path,
376                           ancestor,
377                           ours, our_label,
378                           theirs, their_label, virtual_ancestor);
379 }