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 }