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