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_unused,
  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 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         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("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         struct child_process child;
 179         const char *args[20];
 180         int status, fd, i;
 181         struct stat st;
 182
 183         if (fn->cmdline == NULL)
 184                 die("custom merge driver %s lacks command line.", fn->name);
 185
 186         result->ptr = NULL;
 187         result->size = 0;
 188         create_temp(orig, temp[0]);
 189         create_temp(src1, temp[1]);
 190         create_temp(src2, temp[2]);
 191
 192         strbuf_expand(&cmd, fn->cmdline, strbuf_expand_dict_cb, &dict);
 193
 194         memset(&child, 0, sizeof(child));
 195         child.argv = args;
 196         args[0] = "sh";
 197         args[1] = "-c";
 198         args[2] = cmd.buf;
 199         args[3] = NULL;
 200
 201         status = run_command(&child);
 202         if (status < -ERR_RUN_COMMAND_FORK)
 203                 ; /* failure in run-command */
 204         else
 205                 status = -status;
 206         fd = open(temp[1], O_RDONLY);
 207         if (fd < 0)
 208                 goto bad;
 209         if (fstat(fd, &st))
 210                 goto close_bad;
 211         result->size = st.st_size;
 212         result->ptr = xmalloc(result->size + 1);
 213         if (read_in_full(fd, result->ptr, result->size) != result->size) {
 214                 free(result->ptr);
 215                 result->ptr = NULL;
 216                 result->size = 0;
 217         }
 218  close_bad:
 219         close(fd);
 220  bad:
 221         for (i = 0; i < 3; i++)
 222                 unlink_or_warn(temp[i]);
 223         strbuf_release(&cmd);
 224         return status;
 225 }
 226
 227 /*
 228  * merge.default and merge.driver configuration items
 229  */
 230 static struct ll_merge_driver *ll_user_merge, **ll_user_merge_tail;
 231 static const char *default_ll_merge;
 232
 233 static int read_merge_config(const char *var, const char *value, void *cb)
 234 {
 235         struct ll_merge_driver *fn;
 236         const char *ep, *name;
 237         int namelen;
 238
 239         if (!strcmp(var, "merge.default")) {
 240                 if (value)
 241                         default_ll_merge = strdup(value);
 242                 return 0;
 243         }
 244
 245         /*
 246          * We are not interested in anything but "merge.<name>.variable";
 247          * especially, we do not want to look at variables such as
 248          * "merge.summary", "merge.tool", and "merge.verbosity".
 249          */
 250         if (prefixcmp(var, "merge.") || (ep = strrchr(var, '.')) == var + 5)
 251                 return 0;
 252
 253         /*
 254          * Find existing one as we might be processing merge.<name>.var2
 255          * after seeing merge.<name>.var1.
 256          */
 257         name = var + 6;
 258         namelen = ep - name;
 259         for (fn = ll_user_merge; fn; fn = fn->next)
 260                 if (!strncmp(fn->name, name, namelen) && !fn->name[namelen])
 261                         break;
 262         if (!fn) {
 263                 fn = xcalloc(1, sizeof(struct ll_merge_driver));
 264                 fn->name = xmemdupz(name, namelen);
 265                 fn->fn = ll_ext_merge;
 266                 *ll_user_merge_tail = fn;
 267                 ll_user_merge_tail = &(fn->next);
 268         }
 269
 270         ep++;
 271
 272         if (!strcmp("name", ep)) {
 273                 if (!value)
 274                         return error("%s: lacks value", var);
 275                 fn->description = strdup(value);
 276                 return 0;
 277         }
 278
 279         if (!strcmp("driver", ep)) {
 280                 if (!value)
 281                         return error("%s: lacks value", var);
 282                 /*
 283                  * merge.<name>.driver specifies the command line:
 284                  *
 285                  *      command-line
 286                  *
 287                  * The command-line will be interpolated with the following
 288                  * tokens and is given to the shell:
 289                  *
 290                  *    %O - temporary file name for the merge base.
 291                  *    %A - temporary file name for our version.
 292                  *    %B - temporary file name for the other branches' version.
 293                  *
 294                  * The external merge driver should write the results in the
 295                  * file named by %A, and signal that it has done with zero exit
 296                  * status.
 297                  */
 298                 fn->cmdline = strdup(value);
 299                 return 0;
 300         }
 301
 302         if (!strcmp("recursive", ep)) {
 303                 if (!value)
 304                         return error("%s: lacks value", var);
 305                 fn->recursive = strdup(value);
 306                 return 0;
 307         }
 308
 309         return 0;
 310 }
 311
 312 static void initialize_ll_merge(void)
 313 {
 314         if (ll_user_merge_tail)
 315                 return;
 316         ll_user_merge_tail = &ll_user_merge;
 317         git_config(read_merge_config, NULL);
 318 }
 319
 320 static const struct ll_merge_driver *find_ll_merge_driver(const char *merge_attr)
 321 {
 322         struct ll_merge_driver *fn;
 323         const char *name;
 324         int i;
 325
 326         initialize_ll_merge();
 327
 328         if (ATTR_TRUE(merge_attr))
 329                 return &ll_merge_drv[LL_TEXT_MERGE];
 330         else if (ATTR_FALSE(merge_attr))
 331                 return &ll_merge_drv[LL_BINARY_MERGE];
 332         else if (ATTR_UNSET(merge_attr)) {
 333                 if (!default_ll_merge)
 334                         return &ll_merge_drv[LL_TEXT_MERGE];
 335                 else
 336                         name = default_ll_merge;
 337         }
 338         else
 339                 name = merge_attr;
 340
 341         for (fn = ll_user_merge; fn; fn = fn->next)
 342                 if (!strcmp(fn->name, name))
 343                         return fn;
 344
 345         for (i = 0; i < ARRAY_SIZE(ll_merge_drv); i++)
 346                 if (!strcmp(ll_merge_drv[i].name, name))
 347                         return &ll_merge_drv[i];
 348
 349         /* default to the 3-way */
 350         return &ll_merge_drv[LL_TEXT_MERGE];
 351 }
 352
 353 static const char *git_path_check_merge(const char *path)
 354 {
 355         static struct git_attr_check attr_merge_check;
 356
 357         if (!attr_merge_check.attr)
 358                 attr_merge_check.attr = git_attr("merge", 5);
 359
 360         if (git_checkattr(path, 1, &attr_merge_check))
 361                 return NULL;
 362         return attr_merge_check.value;
 363 }
 364
 365 int ll_merge(mmbuffer_t *result_buf,
 366              const char *path,
 367              mmfile_t *ancestor,
 368              mmfile_t *ours, const char *our_label,
 369              mmfile_t *theirs, const char *their_label,
 370              int virtual_ancestor)
 371 {
 372         const char *ll_driver_name;
 373         const struct ll_merge_driver *driver;
 374
 375         ll_driver_name = git_path_check_merge(path);
 376         driver = find_ll_merge_driver(ll_driver_name);
 377
 378         if (virtual_ancestor && driver->recursive)
 379                 driver = find_ll_merge_driver(driver->recursive);
 380         return driver->fn(driver, result_buf, path,
 381                           ancestor,
 382                           ours, our_label,
 383                           theirs, their_label, virtual_ancestor);
 384 }