merge-tree.con commit Elaborate on why ':' is a bad idea in a ref name. (87a56cd)
   1#include "cache.h"
   2#include "tree-walk.h"
   3
   4static const char merge_tree_usage[] = "git-merge-tree <base-tree> <branch1> <branch2>";
   5static int resolve_directories = 1;
   6
   7static void merge_trees(struct tree_desc t[3], const char *base);
   8
   9/* An empty entry never compares same, not even to another empty entry */
  10static int same_entry(struct name_entry *a, struct name_entry *b)
  11{
  12        return  a->sha1 &&
  13                b->sha1 &&
  14                !memcmp(a->sha1, b->sha1, 20) &&
  15                a->mode == b->mode;
  16}
  17
  18static const char *sha1_to_hex_zero(const unsigned char *sha1)
  19{
  20        if (sha1)
  21                return sha1_to_hex(sha1);
  22        return "0000000000000000000000000000000000000000";
  23}
  24
  25static void resolve(const char *base, struct name_entry *branch1, struct name_entry *result)
  26{
  27        /* If it's already branch1, don't bother showing it */
  28        if (!branch1)
  29                return;
  30
  31        printf("0 %06o->%06o %s->%s %s%s\n",
  32                branch1->mode, result->mode,
  33                sha1_to_hex_zero(branch1->sha1),
  34                sha1_to_hex_zero(result->sha1),
  35                base, result->path);
  36}
  37
  38static int unresolved_directory(const char *base, struct name_entry n[3])
  39{
  40        int baselen;
  41        char *newbase;
  42        struct name_entry *p;
  43        struct tree_desc t[3];
  44        void *buf0, *buf1, *buf2;
  45
  46        if (!resolve_directories)
  47                return 0;
  48        p = n;
  49        if (!p->mode) {
  50                p++;
  51                if (!p->mode)
  52                        p++;
  53        }
  54        if (!S_ISDIR(p->mode))
  55                return 0;
  56        baselen = strlen(base);
  57        newbase = xmalloc(baselen + p->pathlen + 2);
  58        memcpy(newbase, base, baselen);
  59        memcpy(newbase + baselen, p->path, p->pathlen);
  60        memcpy(newbase + baselen + p->pathlen, "/", 2);
  61
  62        buf0 = fill_tree_descriptor(t+0, n[0].sha1);
  63        buf1 = fill_tree_descriptor(t+1, n[1].sha1);
  64        buf2 = fill_tree_descriptor(t+2, n[2].sha1);
  65        merge_trees(t, newbase);
  66
  67        free(buf0);
  68        free(buf1);
  69        free(buf2);
  70        free(newbase);
  71        return 1;
  72}
  73
  74static void unresolved(const char *base, struct name_entry n[3])
  75{
  76        if (unresolved_directory(base, n))
  77                return;
  78        if (n[0].sha1)
  79                printf("1 %06o %s %s%s\n", n[0].mode, sha1_to_hex(n[0].sha1), base, n[0].path);
  80        if (n[1].sha1)
  81                printf("2 %06o %s %s%s\n", n[1].mode, sha1_to_hex(n[1].sha1), base, n[1].path);
  82        if (n[2].sha1)
  83                printf("3 %06o %s %s%s\n", n[2].mode, sha1_to_hex(n[2].sha1), base, n[2].path);
  84}
  85
  86/*
  87 * Merge two trees together (t[1] and t[2]), using a common base (t[0])
  88 * as the origin.
  89 *
  90 * This walks the (sorted) trees in lock-step, checking every possible
  91 * name. Note that directories automatically sort differently from other
  92 * files (see "base_name_compare"), so you'll never see file/directory
  93 * conflicts, because they won't ever compare the same.
  94 *
  95 * IOW, if a directory changes to a filename, it will automatically be
  96 * seen as the directory going away, and the filename being created.
  97 *
  98 * Think of this as a three-way diff.
  99 *
 100 * The output will be either:
 101 *  - successful merge
 102 *       "0 mode sha1 filename"
 103 *    NOTE NOTE NOTE! FIXME! We really really need to walk the index
 104 *    in parallel with this too!
 105 *
 106 *  - conflict:
 107 *      "1 mode sha1 filename"
 108 *      "2 mode sha1 filename"
 109 *      "3 mode sha1 filename"
 110 *    where not all of the 1/2/3 lines may exist, of course.
 111 *
 112 * The successful merge rules are the same as for the three-way merge
 113 * in git-read-tree.
 114 */
 115static void threeway_callback(int n, unsigned long mask, struct name_entry *entry, const char *base)
 116{
 117        /* Same in both? */
 118        if (same_entry(entry+1, entry+2)) {
 119                if (entry[0].sha1) {
 120                        resolve(base, NULL, entry+1);
 121                        return;
 122                }
 123        }
 124
 125        if (same_entry(entry+0, entry+1)) {
 126                if (entry[2].sha1 && !S_ISDIR(entry[2].mode)) {
 127                        resolve(base, entry+1, entry+2);
 128                        return;
 129                }
 130        }
 131
 132        if (same_entry(entry+0, entry+2)) {
 133                if (entry[1].sha1 && !S_ISDIR(entry[1].mode)) {
 134                        resolve(base, NULL, entry+1);
 135                        return;
 136                }
 137        }
 138
 139        unresolved(base, entry);
 140}
 141
 142static void merge_trees(struct tree_desc t[3], const char *base)
 143{
 144        traverse_trees(3, t, base, threeway_callback);
 145}
 146
 147static void *get_tree_descriptor(struct tree_desc *desc, const char *rev)
 148{
 149        unsigned char sha1[20];
 150        void *buf;
 151
 152        if (get_sha1(rev, sha1))
 153                die("unknown rev %s", rev);
 154        buf = fill_tree_descriptor(desc, sha1);
 155        if (!buf)
 156                die("%s is not a tree", rev);
 157        return buf;
 158}
 159
 160int main(int argc, char **argv)
 161{
 162        struct tree_desc t[3];
 163        void *buf1, *buf2, *buf3;
 164
 165        if (argc < 4)
 166                usage(merge_tree_usage);
 167
 168        buf1 = get_tree_descriptor(t+0, argv[1]);
 169        buf2 = get_tree_descriptor(t+1, argv[2]);
 170        buf3 = get_tree_descriptor(t+2, argv[3]);
 171        merge_trees(t, "");
 172        free(buf1);
 173        free(buf2);
 174        free(buf3);
 175        return 0;
 176}