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 }