read-tree.c

   1 /*
   2  * GIT - The information manager from hell
   3  *
   4  * Copyright (C) Linus Torvalds, 2005
   5  */
   6 #include "cache.h"
   7
   8 static int stage = 0;
   9
  10 static int read_one_entry(unsigned char *sha1, const char *base, int baselen, const char *pathname, unsigned mode)
  11 {
  12         int len = strlen(pathname);
  13         unsigned int size = cache_entry_size(baselen + len);
  14         struct cache_entry *ce = malloc(size);
  15
  16         memset(ce, 0, size);
  17
  18         ce->ce_mode = htonl(mode);
  19         ce->ce_flags = create_ce_flags(baselen + len, stage);
  20         memcpy(ce->name, base, baselen);
  21         memcpy(ce->name + baselen, pathname, len+1);
  22         memcpy(ce->sha1, sha1, 20);
  23         return add_cache_entry(ce, 1);
  24 }
  25
  26 static int read_tree(unsigned char *sha1, const char *base, int baselen)
  27 {
  28         void *buffer;
  29         unsigned long size;
  30         char type[20];
  31
  32         buffer = read_sha1_file(sha1, type, &size);
  33         if (!buffer)
  34                 return -1;
  35         if (strcmp(type, "tree"))
  36                 return -1;
  37         while (size) {
  38                 int len = strlen(buffer)+1;
  39                 unsigned char *sha1 = buffer + len;
  40                 char *path = strchr(buffer, ' ')+1;
  41                 unsigned int mode;
  42
  43                 if (size < len + 20 || sscanf(buffer, "%o", &mode) != 1)
  44                         return -1;
  45
  46                 buffer = sha1 + 20;
  47                 size -= len + 20;
  48
  49                 if (S_ISDIR(mode)) {
  50                         int retval;
  51                         int pathlen = strlen(path);
  52                         char *newbase = malloc(baselen + 1 + pathlen);
  53                         memcpy(newbase, base, baselen);
  54                         memcpy(newbase + baselen, path, pathlen);
  55                         newbase[baselen + pathlen] = '/';
  56                         retval = read_tree(sha1, newbase, baselen + pathlen + 1);
  57                         free(newbase);
  58                         if (retval)
  59                                 return -1;
  60                         continue;
  61                 }
  62                 if (read_one_entry(sha1, base, baselen, path, mode) < 0)
  63                         return -1;
  64         }
  65         return 0;
  66 }
  67
  68 static int remove_lock = 0;
  69
  70 static void remove_lock_file(void)
  71 {
  72         if (remove_lock)
  73                 unlink(".git/index.lock");
  74 }
  75
  76 /*
  77  * This removes all identical entries and collapses them to state 0.
  78  *
  79  * _Any_ other merge (even a trivial one, like both ) is left to user policy.
  80  * That includes "both created the same file", and "both removed the same
  81  * file" - which are trivial, but the user might still want to _note_ it.
  82  */
  83 static int same_entry(struct cache_entry *a,
  84                         struct cache_entry *b,
  85                         struct cache_entry *c)
  86 {
  87         int len = ce_namelen(a);
  88         return  a->ce_mode == b->ce_mode &&
  89                 a->ce_mode == c->ce_mode &&
  90                 ce_namelen(b) == len &&
  91                 ce_namelen(c) == len &&
  92                 !memcmp(a->name, b->name, len) &&
  93                 !memcmp(a->name, c->name, len) &&
  94                 !memcmp(a->sha1, b->sha1, 20) &&
  95                 !memcmp(a->sha1, c->sha1, 20);
  96 }
  97
  98 static void trivially_merge_cache(struct cache_entry **src, int nr)
  99 {
 100         struct cache_entry **dst = src;
 101
 102         while (nr) {
 103                 struct cache_entry *ce;
 104
 105                 ce = src[0];
 106                 if (nr > 2 && same_entry(ce, src[1], src[2])) {
 107                         ce->ce_flags &= ~htons(CE_STAGEMASK);
 108                         src += 2;
 109                         nr -= 2;
 110                         active_nr -= 2;
 111                 }
 112                 *dst = ce;
 113                 src++;
 114                 dst++;
 115                 nr--;
 116         }
 117 }
 118
 119 int main(int argc, char **argv)
 120 {
 121         int i, newfd;
 122         unsigned char sha1[20];
 123
 124         newfd = open(".git/index.lock", O_RDWR | O_CREAT | O_EXCL, 0600);
 125         if (newfd < 0)
 126                 die("unable to create new cachefile");
 127         atexit(remove_lock_file);
 128         remove_lock = 1;
 129
 130         for (i = 1; i < argc; i++) {
 131                 const char *arg = argv[i];
 132
 133                 /* "-m" stands for "merge", meaning we start in stage 1 */
 134                 if (!strcmp(arg, "-m")) {
 135                         stage = 1;
 136                         continue;
 137                 }
 138                 if (get_sha1_hex(arg, sha1) < 0)
 139                         usage("read-tree [-m] <sha1>");
 140                 if (stage > 3)
 141                         usage("can't merge more than two trees");
 142                 if (read_tree(sha1, "", 0) < 0)
 143                         die("failed to unpack tree object %s", arg);
 144                 stage++;
 145         }
 146         if (stage == 4)
 147                 trivially_merge_cache(active_cache, active_nr);
 148         if (write_cache(newfd, active_cache, active_nr) ||
 149             rename(".git/index.lock", ".git/index"))
 150                 die("unable to write new index file");
 151         remove_lock = 0;
 152         return 0;
 153 }