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                            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 virtual_ancestor, 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 = 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,
  60                         mmfile_t *orig,
  61                         mmfile_t *src1, const char *name1,
  62                         mmfile_t *src2, const char *name2,
  63                         int virtual_ancestor, int marker_size)
  64 {
  65         xmparam_t xmp;
  66         int style = 0;
  67
  68         if (buffer_is_binary(orig->ptr, orig->size) ||
  69             buffer_is_binary(src1->ptr, src1->size) ||
  70             buffer_is_binary(src2->ptr, src2->size)) {
  71                 warning("Cannot merge binary files: %s (%s vs. %s)\n",
  72                         path, name1, name2);
  73                 return ll_binary_merge(drv_unused, result,
  74                                        path,
  75                                        orig, src1, name1,
  76                                        src2, name2,
  77                                        virtual_ancestor, marker_size);
  78         }
  79
  80         memset(&xmp, 0, sizeof(xmp));
  81         if (git_xmerge_style >= 0)
  82                 style = git_xmerge_style;
  83         if (marker_size > 0)
  84                 xmp.marker_size = marker_size;
  85         return xdl_merge(orig,
  86                          src1, name1,
  87                          src2, name2,
  88                          &xmp, XDL_MERGE_ZEALOUS | style,
  89                          result);
  90 }
  91
  92 static int ll_union_merge(const struct ll_merge_driver *drv_unused,
  93                           mmbuffer_t *result,
  94                           const char *path_unused,
  95                           mmfile_t *orig,
  96                           mmfile_t *src1, const char *name1,
  97                           mmfile_t *src2, const char *name2,
  98                           int virtual_ancestor, int marker_size)
  99 {
 100         char *src, *dst;
 101         long size;
 102         int status, saved_style;
 103
 104         /* We have to force the RCS "merge" style */
 105         saved_style = git_xmerge_style;
 106         git_xmerge_style = 0;
 107         status = ll_xdl_merge(drv_unused, result, path_unused,
 108                               orig, src1, NULL, src2, NULL,
 109                               virtual_ancestor, marker_size);
 110         git_xmerge_style = saved_style;
 111         if (status <= 0)
 112                 return status;
 113         size = result->size;
 114         src = dst = result->ptr;
 115         while (size) {
 116                 char ch;
 117                 if ((marker_size < size) &&
 118                     (*src == '<' || *src == '=' || *src == '>')) {
 119                         int i;
 120                         ch = *src;
 121                         for (i = 0; i < marker_size; i++)
 122                                 if (src[i] != ch)
 123                                         goto not_a_marker;
 124                         if (src[marker_size] != '\n')
 125                                 goto not_a_marker;
 126                         src += marker_size + 1;
 127                         size -= marker_size + 1;
 128                         continue;
 129                 }
 130         not_a_marker:
 131                 do {
 132                         ch = *src++;
 133                         *dst++ = ch;
 134                         size--;
 135                 } while (ch != '\n' && size);
 136         }
 137         result->size = dst - result->ptr;
 138         return 0;
 139 }
 140
 141 #define LL_BINARY_MERGE 0
 142 #define LL_TEXT_MERGE 1
 143 #define LL_UNION_MERGE 2
 144 static struct ll_merge_driver ll_merge_drv[] = {
 145         { "binary", "built-in binary merge", ll_binary_merge },
 146         { "text", "built-in 3-way text merge", ll_xdl_merge },
 147         { "union", "built-in union merge", ll_union_merge },
 148 };
 149
 150 static void create_temp(mmfile_t *src, char *path)
 151 {
 152         int fd;
 153
 154         strcpy(path, ".merge_file_XXXXXX");
 155         fd = xmkstemp(path);
 156         if (write_in_full(fd, src->ptr, src->size) != src->size)
 157                 die_errno("unable to write temp-file");
 158         close(fd);
 159 }
 160
 161 /*
 162  * User defined low-level merge driver support.
 163  */
 164 static int ll_ext_merge(const struct ll_merge_driver *fn,
 165                         mmbuffer_t *result,
 166                         const char *path,
 167                         mmfile_t *orig,
 168                         mmfile_t *src1, const char *name1,
 169                         mmfile_t *src2, const char *name2,
 170                         int virtual_ancestor, int marker_size)
 171 {
 172         char temp[4][50];
 173         struct strbuf cmd = STRBUF_INIT;
 174         struct strbuf_expand_dict_entry dict[] = {
 175                 { "O", temp[0] },
 176                 { "A", temp[1] },
 177                 { "B", temp[2] },
 178                 { "L", temp[3] },
 179                 { NULL }
 180         };
 181         const char *args[] = { "sh", "-c", NULL, NULL };
 182         int status, fd, i;
 183         struct stat st;
 184
 185         if (fn->cmdline == NULL)
 186                 die("custom merge driver %s lacks command line.", fn->name);
 187
 188         result->ptr = NULL;
 189         result->size = 0;
 190         create_temp(orig, temp[0]);
 191         create_temp(src1, temp[1]);
 192         create_temp(src2, temp[2]);
 193         sprintf(temp[3], "%d", marker_size);
 194
 195         strbuf_expand(&cmd, fn->cmdline, strbuf_expand_dict_cb, &dict);
 196
 197         args[2] = cmd.buf;
 198         status = run_command_v_opt(args, 0);
 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                  *    %L - conflict marker length
 287                  *
 288                  * The external merge driver should write the results in the
 289                  * file named by %A, and signal that it has done with zero exit
 290                  * status.
 291                  */
 292                 fn->cmdline = xstrdup(value);
 293                 return 0;
 294         }
 295
 296         if (!strcmp("recursive", ep)) {
 297                 if (!value)
 298                         return error("%s: lacks value", var);
 299                 fn->recursive = xstrdup(value);
 300                 return 0;
 301         }
 302
 303         return 0;
 304 }
 305
 306 static void initialize_ll_merge(void)
 307 {
 308         if (ll_user_merge_tail)
 309                 return;
 310         ll_user_merge_tail = &ll_user_merge;
 311         git_config(read_merge_config, NULL);
 312 }
 313
 314 static const struct ll_merge_driver *find_ll_merge_driver(const char *merge_attr)
 315 {
 316         struct ll_merge_driver *fn;
 317         const char *name;
 318         int i;
 319
 320         initialize_ll_merge();
 321
 322         if (ATTR_TRUE(merge_attr))
 323                 return &ll_merge_drv[LL_TEXT_MERGE];
 324         else if (ATTR_FALSE(merge_attr))
 325                 return &ll_merge_drv[LL_BINARY_MERGE];
 326         else if (ATTR_UNSET(merge_attr)) {
 327                 if (!default_ll_merge)
 328                         return &ll_merge_drv[LL_TEXT_MERGE];
 329                 else
 330                         name = default_ll_merge;
 331         }
 332         else
 333                 name = merge_attr;
 334
 335         for (fn = ll_user_merge; fn; fn = fn->next)
 336                 if (!strcmp(fn->name, name))
 337                         return fn;
 338
 339         for (i = 0; i < ARRAY_SIZE(ll_merge_drv); i++)
 340                 if (!strcmp(ll_merge_drv[i].name, name))
 341                         return &ll_merge_drv[i];
 342
 343         /* default to the 3-way */
 344         return &ll_merge_drv[LL_TEXT_MERGE];
 345 }
 346
 347 static int git_path_check_merge(const char *path, struct git_attr_check check[2])
 348 {
 349         if (!check[0].attr) {
 350                 check[0].attr = git_attr("merge");
 351                 check[1].attr = git_attr("conflict-marker-size");
 352         }
 353         return git_checkattr(path, 2, check);
 354 }
 355
 356 int ll_merge(mmbuffer_t *result_buf,
 357              const char *path,
 358              mmfile_t *ancestor,
 359              mmfile_t *ours, const char *our_label,
 360              mmfile_t *theirs, const char *their_label,
 361              int virtual_ancestor)
 362 {
 363         static struct git_attr_check check[2];
 364         const char *ll_driver_name = NULL;
 365         int marker_size = DEFAULT_CONFLICT_MARKER_SIZE;
 366         const struct ll_merge_driver *driver;
 367
 368         if (!git_path_check_merge(path, check)) {
 369                 ll_driver_name = check[0].value;
 370                 if (check[1].value) {
 371                         marker_size = atoi(check[1].value);
 372                         if (marker_size <= 0)
 373                                 marker_size = DEFAULT_CONFLICT_MARKER_SIZE;
 374                 }
 375         }
 376         driver = find_ll_merge_driver(ll_driver_name);
 377         if (virtual_ancestor && driver->recursive)
 378                 driver = find_ll_merge_driver(driver->recursive);
 379         return driver->fn(driver, result_buf, path, ancestor,
 380                           ours, our_label, theirs, their_label,
 381                           virtual_ancestor, marker_size);
 382 }
 383
 384 int ll_merge_marker_size(const char *path)
 385 {
 386         static struct git_attr_check check;
 387         int marker_size = DEFAULT_CONFLICT_MARKER_SIZE;
 388
 389         if (!check.attr)
 390                 check.attr = git_attr("conflict-marker-size");
 391         if (!git_checkattr(path, 1, &check) && check.value) {
 392                 marker_size = atoi(check.value);
 393                 if (marker_size <= 0)
 394                         marker_size = DEFAULT_CONFLICT_MARKER_SIZE;
 395         }
 396         return marker_size;
 397 }