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         fd = open(temp[1], O_RDONLY);
 196         if (fd < 0)
 197                 goto bad;
 198         if (fstat(fd, &st))
 199                 goto close_bad;
 200         result->size = st.st_size;
 201         result->ptr = xmalloc(result->size + 1);
 202         if (read_in_full(fd, result->ptr, result->size) != result->size) {
 203                 free(result->ptr);
 204                 result->ptr = NULL;
 205                 result->size = 0;
 206         }
 207  close_bad:
 208         close(fd);
 209  bad:
 210         for (i = 0; i < 3; i++)
 211                 unlink_or_warn(temp[i]);
 212         strbuf_release(&cmd);
 213         return status;
 214 }
 215
 216 /*
 217  * merge.default and merge.driver configuration items
 218  */
 219 static struct ll_merge_driver *ll_user_merge, **ll_user_merge_tail;
 220 static const char *default_ll_merge;
 221
 222 static int read_merge_config(const char *var, const char *value, void *cb)
 223 {
 224         struct ll_merge_driver *fn;
 225         const char *ep, *name;
 226         int namelen;
 227
 228         if (!strcmp(var, "merge.default")) {
 229                 if (value)
 230                         default_ll_merge = xstrdup(value);
 231                 return 0;
 232         }
 233
 234         /*
 235          * We are not interested in anything but "merge.<name>.variable";
 236          * especially, we do not want to look at variables such as
 237          * "merge.summary", "merge.tool", and "merge.verbosity".
 238          */
 239         if (prefixcmp(var, "merge.") || (ep = strrchr(var, '.')) == var + 5)
 240                 return 0;
 241
 242         /*
 243          * Find existing one as we might be processing merge.<name>.var2
 244          * after seeing merge.<name>.var1.
 245          */
 246         name = var + 6;
 247         namelen = ep - name;
 248         for (fn = ll_user_merge; fn; fn = fn->next)
 249                 if (!strncmp(fn->name, name, namelen) && !fn->name[namelen])
 250                         break;
 251         if (!fn) {
 252                 fn = xcalloc(1, sizeof(struct ll_merge_driver));
 253                 fn->name = xmemdupz(name, namelen);
 254                 fn->fn = ll_ext_merge;
 255                 *ll_user_merge_tail = fn;
 256                 ll_user_merge_tail = &(fn->next);
 257         }
 258
 259         ep++;
 260
 261         if (!strcmp("name", ep)) {
 262                 if (!value)
 263                         return error("%s: lacks value", var);
 264                 fn->description = xstrdup(value);
 265                 return 0;
 266         }
 267
 268         if (!strcmp("driver", ep)) {
 269                 if (!value)
 270                         return error("%s: lacks value", var);
 271                 /*
 272                  * merge.<name>.driver specifies the command line:
 273                  *
 274                  *      command-line
 275                  *
 276                  * The command-line will be interpolated with the following
 277                  * tokens and is given to the shell:
 278                  *
 279                  *    %O - temporary file name for the merge base.
 280                  *    %A - temporary file name for our version.
 281                  *    %B - temporary file name for the other branches' version.
 282                  *
 283                  * The external merge driver should write the results in the
 284                  * file named by %A, and signal that it has done with zero exit
 285                  * status.
 286                  */
 287                 fn->cmdline = xstrdup(value);
 288                 return 0;
 289         }
 290
 291         if (!strcmp("recursive", ep)) {
 292                 if (!value)
 293                         return error("%s: lacks value", var);
 294                 fn->recursive = xstrdup(value);
 295                 return 0;
 296         }
 297
 298         return 0;
 299 }
 300
 301 static void initialize_ll_merge(void)
 302 {
 303         if (ll_user_merge_tail)
 304                 return;
 305         ll_user_merge_tail = &ll_user_merge;
 306         git_config(read_merge_config, NULL);
 307 }
 308
 309 static const struct ll_merge_driver *find_ll_merge_driver(const char *merge_attr)
 310 {
 311         struct ll_merge_driver *fn;
 312         const char *name;
 313         int i;
 314
 315         initialize_ll_merge();
 316
 317         if (ATTR_TRUE(merge_attr))
 318                 return &ll_merge_drv[LL_TEXT_MERGE];
 319         else if (ATTR_FALSE(merge_attr))
 320                 return &ll_merge_drv[LL_BINARY_MERGE];
 321         else if (ATTR_UNSET(merge_attr)) {
 322                 if (!default_ll_merge)
 323                         return &ll_merge_drv[LL_TEXT_MERGE];
 324                 else
 325                         name = default_ll_merge;
 326         }
 327         else
 328                 name = merge_attr;
 329
 330         for (fn = ll_user_merge; fn; fn = fn->next)
 331                 if (!strcmp(fn->name, name))
 332                         return fn;
 333
 334         for (i = 0; i < ARRAY_SIZE(ll_merge_drv); i++)
 335                 if (!strcmp(ll_merge_drv[i].name, name))
 336                         return &ll_merge_drv[i];
 337
 338         /* default to the 3-way */
 339         return &ll_merge_drv[LL_TEXT_MERGE];
 340 }
 341
 342 static const char *git_path_check_merge(const char *path)
 343 {
 344         static struct git_attr_check attr_merge_check;
 345
 346         if (!attr_merge_check.attr)
 347                 attr_merge_check.attr = git_attr("merge", 5);
 348
 349         if (git_checkattr(path, 1, &attr_merge_check))
 350                 return NULL;
 351         return attr_merge_check.value;
 352 }
 353
 354 int ll_merge(mmbuffer_t *result_buf,
 355              const char *path,
 356              mmfile_t *ancestor,
 357              mmfile_t *ours, const char *our_label,
 358              mmfile_t *theirs, const char *their_label,
 359              int virtual_ancestor)
 360 {
 361         const char *ll_driver_name;
 362         const struct ll_merge_driver *driver;
 363
 364         ll_driver_name = git_path_check_merge(path);
 365         driver = find_ll_merge_driver(ll_driver_name);
 366
 367         if (virtual_ancestor && driver->recursive)
 368                 driver = find_ll_merge_driver(driver->recursive);
 369         return driver->fn(driver, result_buf, path,
 370                           ancestor,
 371                           ours, our_label,
 372                           theirs, their_label, virtual_ancestor);
 373 }