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         char branch1_sha1[50];
  28
  29         /* If it's already branch1, don't bother showing it */
  30         if (!branch1)
  31                 return;
  32         memcpy(branch1_sha1, sha1_to_hex_zero(branch1->sha1), 41);
  33
  34         printf("0 %06o->%06o %s->%s %s%s\n",
  35                 branch1->mode, result->mode,
  36                 branch1_sha1, sha1_to_hex_zero(result->sha1),
  37                 base, result->path);
  38 }
  39
  40 static int unresolved_directory(const char *base, struct name_entry n[3])
  41 {
  42         int baselen;
  43         char *newbase;
  44         struct name_entry *p;
  45         struct tree_desc t[3];
  46         void *buf0, *buf1, *buf2;
  47
  48         if (!resolve_directories)
  49                 return 0;
  50         p = n;
  51         if (!p->mode) {
  52                 p++;
  53                 if (!p->mode)
  54                         p++;
  55         }
  56         if (!S_ISDIR(p->mode))
  57                 return 0;
  58         baselen = strlen(base);
  59         newbase = xmalloc(baselen + p->pathlen + 2);
  60         memcpy(newbase, base, baselen);
  61         memcpy(newbase + baselen, p->path, p->pathlen);
  62         memcpy(newbase + baselen + p->pathlen, "/", 2);
  63
  64         buf0 = fill_tree_descriptor(t+0, n[0].sha1);
  65         buf1 = fill_tree_descriptor(t+1, n[1].sha1);
  66         buf2 = fill_tree_descriptor(t+2, n[2].sha1);
  67         merge_trees(t, newbase);
  68
  69         free(buf0);
  70         free(buf1);
  71         free(buf2);
  72         free(newbase);
  73         return 1;
  74 }
  75
  76 static void unresolved(const char *base, struct name_entry n[3])
  77 {
  78         if (unresolved_directory(base, n))
  79                 return;
  80         if (n[0].sha1)
  81                 printf("1 %06o %s %s%s\n", n[0].mode, sha1_to_hex(n[0].sha1), base, n[0].path);
  82         if (n[1].sha1)
  83                 printf("2 %06o %s %s%s\n", n[1].mode, sha1_to_hex(n[1].sha1), base, n[1].path);
  84         if (n[2].sha1)
  85                 printf("3 %06o %s %s%s\n", n[2].mode, sha1_to_hex(n[2].sha1), base, n[2].path);
  86 }
  87
  88 /*
  89  * Merge two trees together (t[1] and t[2]), using a common base (t[0])
  90  * as the origin.
  91  *
  92  * This walks the (sorted) trees in lock-step, checking every possible
  93  * name. Note that directories automatically sort differently from other
  94  * files (see "base_name_compare"), so you'll never see file/directory
  95  * conflicts, because they won't ever compare the same.
  96  *
  97  * IOW, if a directory changes to a filename, it will automatically be
  98  * seen as the directory going away, and the filename being created.
  99  *
 100  * Think of this as a three-way diff.
 101  *
 102  * The output will be either:
 103  *  - successful merge
 104  *       "0 mode sha1 filename"
 105  *    NOTE NOTE NOTE! FIXME! We really really need to walk the index
 106  *    in parallel with this too!
 107  *
 108  *  - conflict:
 109  *      "1 mode sha1 filename"
 110  *      "2 mode sha1 filename"
 111  *      "3 mode sha1 filename"
 112  *    where not all of the 1/2/3 lines may exist, of course.
 113  *
 114  * The successful merge rules are the same as for the three-way merge
 115  * in git-read-tree.
 116  */
 117 static void threeway_callback(int n, unsigned long mask, struct name_entry *entry, const char *base)
 118 {
 119         /* Same in both? */
 120         if (same_entry(entry+1, entry+2)) {
 121                 if (entry[0].sha1) {
 122                         resolve(base, NULL, entry+1);
 123                         return;
 124                 }
 125         }
 126
 127         if (same_entry(entry+0, entry+1)) {
 128                 if (entry[2].sha1 && !S_ISDIR(entry[2].mode)) {
 129                         resolve(base, entry+1, entry+2);
 130                         return;
 131                 }
 132         }
 133
 134         if (same_entry(entry+0, entry+2)) {
 135                 if (entry[1].sha1 && !S_ISDIR(entry[1].mode)) {
 136                         resolve(base, NULL, entry+1);
 137                         return;
 138                 }
 139         }
 140
 141         unresolved(base, entry);
 142 }
 143
 144 static void merge_trees(struct tree_desc t[3], const char *base)
 145 {
 146         traverse_trees(3, t, base, threeway_callback);
 147 }
 148
 149 static void *get_tree_descriptor(struct tree_desc *desc, const char *rev)
 150 {
 151         unsigned char sha1[20];
 152         void *buf;
 153
 154         if (get_sha1(rev, sha1) < 0)
 155                 die("unknown rev %s", rev);
 156         buf = fill_tree_descriptor(desc, sha1);
 157         if (!buf)
 158                 die("%s is not a tree", rev);
 159         return buf;
 160 }
 161
 162 int main(int argc, char **argv)
 163 {
 164         struct tree_desc t[3];
 165         void *buf1, *buf2, *buf3;
 166
 167         if (argc < 4)
 168                 usage(merge_tree_usage);
 169
 170         buf1 = get_tree_descriptor(t+0, argv[1]);
 171         buf2 = get_tree_descriptor(t+1, argv[2]);
 172         buf3 = get_tree_descriptor(t+2, argv[3]);
 173         merge_trees(t, "");
 174         free(buf1);
 175         free(buf2);
 176         free(buf3);
 177         return 0;
 178 }