merge-tree.c

   1 #include "cache.h"
   2 #include "tree-walk.h"
   3
   4 static const char merge_tree_usage[] = "git-merge-tree <base-tree> <branch1> <branch2>";
   5 static int resolve_directories = 1;
   6
   7 static 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 */
  10 static 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
  18 static 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
  25 static 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
  38 static 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
  74 static 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  */
 115 static 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
 142 static void merge_trees(struct tree_desc t[3], const char *base)
 143 {
 144         traverse_trees(3, t, base, threeway_callback);
 145 }
 146
 147 static 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
 160 int 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 }