+/*
+ * GIT - The information manager from hell
+ *
+ * Copyright (C) Linus Torvalds, 2005
+ */
#include "cache.h"
-static int unpack(unsigned char *sha1)
+static int stage = 0;
+static int update = 0;
+
+static int unpack_tree(unsigned char *sha1)
{
void *buffer;
unsigned long size;
- char type[20];
+ int ret;
- buffer = read_sha1_file(sha1, type, &size);
+ buffer = read_object_with_reference(sha1, "tree", &size, NULL);
if (!buffer)
- usage("unable to read sha1 file");
- if (strcmp(type, "tree"))
- usage("expected a 'tree' node");
- while (size) {
- int len = strlen(buffer)+1;
- unsigned char *sha1 = buffer + len;
- char *path = strchr(buffer, ' ')+1;
- unsigned int mode;
- if (size < len + 20 || sscanf(buffer, "%o", &mode) != 1)
- usage("corrupt 'tree' file");
- buffer = sha1 + 20;
- size -= len + 20;
- printf("%o %s (%s)\n", mode, path, sha1_to_hex(sha1));
+ return -1;
+ ret = read_tree(buffer, size, stage);
+ free(buffer);
+ return ret;
+}
+
+static char *lockfile_name;
+
+static void remove_lock_file(void)
+{
+ if (lockfile_name)
+ unlink(lockfile_name);
+}
+
+static int path_matches(struct cache_entry *a, struct cache_entry *b)
+{
+ int len = ce_namelen(a);
+ return ce_namelen(b) == len &&
+ !memcmp(a->name, b->name, len);
+}
+
+static int same(struct cache_entry *a, struct cache_entry *b)
+{
+ return a->ce_mode == b->ce_mode &&
+ !memcmp(a->sha1, b->sha1, 20);
+}
+
+
+/*
+ * This removes all trivial merges that don't change the tree
+ * and collapses them to state 0.
+ *
+ * _Any_ other merge is left to user policy. That includes "both
+ * created the same file", and "both removed the same file" - which are
+ * trivial, but the user might still want to _note_ it.
+ */
+static struct cache_entry *merge_entries(struct cache_entry *a,
+ struct cache_entry *b,
+ struct cache_entry *c)
+{
+ int len = ce_namelen(a);
+
+ /*
+ * Are they all the same filename? We won't do
+ * any name merging
+ */
+ if (ce_namelen(b) != len ||
+ ce_namelen(c) != len ||
+ memcmp(a->name, b->name, len) ||
+ memcmp(a->name, c->name, len))
+ return NULL;
+
+ /*
+ * Ok, all three entries describe the same
+ * filename, but maybe the contents or file
+ * mode have changed?
+ *
+ * The trivial cases end up being the ones where two
+ * out of three files are the same:
+ * - both destinations the same, trivially take either
+ * - one of the destination versions hasn't changed,
+ * take the other.
+ *
+ * The "all entries exactly the same" case falls out as
+ * a special case of any of the "two same" cases.
+ *
+ * Here "a" is "original", and "b" and "c" are the two
+ * trees we are merging.
+ */
+ if (same(b,c))
+ return c;
+ if (same(a,b))
+ return c;
+ if (same(a,c))
+ return b;
+ return NULL;
+}
+
+/*
+ * When a CE gets turned into an unmerged entry, we
+ * want it to be up-to-date
+ */
+static void verify_uptodate(struct cache_entry *ce)
+{
+ struct stat st;
+
+ if (!lstat(ce->name, &st)) {
+ unsigned changed = ce_match_stat(ce, &st);
+ if (!changed)
+ return;
+ errno = 0;
}
- return 0;
+ if (errno == ENOENT)
+ return;
+ die("Entry '%s' not uptodate. Cannot merge.", ce->name);
}
+/*
+ * If the old tree contained a CE that isn't even in the
+ * result, that's always a problem, regardless of whether
+ * it's up-to-date or not (ie it can be a file that we
+ * have updated but not committed yet).
+ */
+static void reject_merge(struct cache_entry *ce)
+{
+ die("Entry '%s' would be overwritten by merge. Cannot merge.", ce->name);
+}
+
+#define CHECK_OLD(ce) if (old && same(old, ce)) { verify_uptodate(old); old = NULL; }
+
+static void trivially_merge_cache(struct cache_entry **src, int nr)
+{
+ struct cache_entry **dst = src;
+ struct cache_entry *old = NULL;
+
+ while (nr--) {
+ struct cache_entry *ce, *result;
+
+ ce = *src++;
+
+ /* We throw away original cache entries except for the stat information */
+ if (!ce_stage(ce)) {
+ if (old)
+ reject_merge(old);
+ old = ce;
+ active_nr--;
+ continue;
+ }
+ if (old && !path_matches(old, ce))
+ reject_merge(old);
+ if (nr > 2 && (result = merge_entries(ce, src[1], src[2])) != NULL) {
+ result->ce_flags |= htons(CE_UPDATE);
+ /*
+ * See if we can re-use the old CE directly?
+ * That way we get the uptodate stat info.
+ *
+ * This also removes the UPDATE flag on
+ * a match.
+ */
+ if (old && same(old, result)) {
+ *result = *old;
+ old = NULL;
+ }
+ CHECK_OLD(ce);
+ CHECK_OLD(src[1]);
+ CHECK_OLD(src[2]);
+ ce = result;
+ ce->ce_flags &= ~htons(CE_STAGEMASK);
+ src += 2;
+ nr -= 2;
+ active_nr -= 2;
+ }
+
+ /*
+ * If we had an old entry that we now effectively
+ * overwrite, make sure it wasn't dirty.
+ */
+ CHECK_OLD(ce);
+ *dst++ = ce;
+ }
+ if (old)
+ reject_merge(old);
+}
+
+/*
+ * Two-way merge.
+ *
+ * The rule is:
+ * - every current entry has to match the old tree
+ * - if the current entry matches the new tree, we leave it
+ * as-is. Otherwise we require that it be up-to-date.
+ */
+static void twoway_merge(struct cache_entry **src, int nr)
+{
+ static struct cache_entry null_entry;
+ struct cache_entry *old = NULL, *stat = &null_entry;
+ struct cache_entry **dst = src;
+
+ while (nr--) {
+ struct cache_entry *ce = *src++;
+ int stage = ce_stage(ce);
+
+ switch (stage) {
+ case 0:
+ if (old)
+ reject_merge(old);
+ old = ce;
+ stat = ce;
+ active_nr--;
+ continue;
+
+ case 1:
+ active_nr--;
+ if (!old)
+ continue;
+ if (!path_matches(old, ce) || !same(old, ce))
+ reject_merge(old);
+ continue;
+
+ case 2:
+ ce->ce_flags |= htons(CE_UPDATE);
+ if (old) {
+ if (!path_matches(old, ce))
+ reject_merge(old);
+ /*
+ * This also removes the UPDATE flag on
+ * a match
+ */
+ if (same(old, ce))
+ *ce = *old;
+ else
+ verify_uptodate(old);
+ old = NULL;
+ }
+ ce->ce_flags &= ~htons(CE_STAGEMASK);
+ *dst++ = ce;
+ continue;
+ }
+ die("impossible two-way stage");
+ }
+ if (old)
+ reject_merge(old);
+}
+
+static void merge_stat_info(struct cache_entry **src, int nr)
+{
+ static struct cache_entry null_entry;
+ struct cache_entry **dst = src;
+ struct cache_entry *stat = &null_entry;
+
+ while (nr--) {
+ struct cache_entry *ce = *src++;
+
+ /* We throw away original cache entries except for the stat information */
+ if (!ce_stage(ce)) {
+ stat = ce;
+ active_nr--;
+ continue;
+ }
+ if (path_matches(ce, stat) && same(ce, stat))
+ *ce = *stat;
+ ce->ce_flags &= ~htons(CE_STAGEMASK);
+ *dst++ = ce;
+ }
+}
+
+static void check_updates(struct cache_entry **src, int nr)
+{
+ static struct checkout state = {
+ .base_dir = "",
+ .force = 1,
+ .quiet = 1,
+ .refresh_cache = 1,
+ };
+ unsigned short mask = htons(CE_UPDATE);
+ while (nr--) {
+ struct cache_entry *ce = *src++;
+ if (ce->ce_flags & mask) {
+ ce->ce_flags &= ~mask;
+ if (update)
+ checkout_entry(ce, &state);
+ }
+ }
+}
+
+static char *read_tree_usage = "git-read-tree (<sha> | -m <sha1> [<sha2> [<sha3>]])";
+
int main(int argc, char **argv)
{
- int fd;
+ int i, newfd, merge;
unsigned char sha1[20];
+ static char lockfile[MAXPATHLEN+1];
+ const char *indexfile = get_index_file();
+
+ snprintf(lockfile, sizeof(lockfile), "%s.lock", indexfile);
+
+ newfd = open(lockfile, O_RDWR | O_CREAT | O_EXCL, 0600);
+ if (newfd < 0)
+ die("unable to create new cachefile");
+ atexit(remove_lock_file);
+ lockfile_name = lockfile;
+
+ merge = 0;
+ for (i = 1; i < argc; i++) {
+ const char *arg = argv[i];
- if (argc != 2)
- usage("read-tree <key>");
- if (get_sha1_hex(argv[1], sha1) < 0)
- usage("read-tree <key>");
- sha1_file_directory = getenv(DB_ENVIRONMENT);
- if (!sha1_file_directory)
- sha1_file_directory = DEFAULT_DB_ENVIRONMENT;
- if (unpack(sha1) < 0)
- usage("unpack failed");
+ /* "-u" means "update", meaning that a merge will update the working directory */
+ if (!strcmp(arg, "-u")) {
+ update = 1;
+ continue;
+ }
+
+ /* "-m" stands for "merge", meaning we start in stage 1 */
+ if (!strcmp(arg, "-m")) {
+ int i;
+ if (stage)
+ die("-m needs to come first");
+ read_cache();
+ for (i = 0; i < active_nr; i++) {
+ if (ce_stage(active_cache[i]))
+ die("you need to resolve your current index first");
+ }
+ stage = 1;
+ merge = 1;
+ continue;
+ }
+ if (get_sha1(arg, sha1) < 0)
+ usage(read_tree_usage);
+ if (stage > 3)
+ usage(read_tree_usage);
+ if (unpack_tree(sha1) < 0)
+ die("failed to unpack tree object %s", arg);
+ stage++;
+ }
+ if (merge) {
+ switch (stage) {
+ case 4: /* Three-way merge */
+ trivially_merge_cache(active_cache, active_nr);
+ check_updates(active_cache, active_nr);
+ break;
+ case 3: /* Update from one tree to another */
+ twoway_merge(active_cache, active_nr);
+ check_updates(active_cache, active_nr);
+ break;
+ case 2: /* Just read a tree, merge with old cache contents */
+ merge_stat_info(active_cache, active_nr);
+ break;
+ default:
+ die("just how do you expect me to merge %d trees?", stage-1);
+ }
+ }
+ if (write_cache(newfd, active_cache, active_nr) || rename(lockfile, indexfile))
+ die("unable to write new index file");
+ lockfile_name = NULL;
return 0;
}
projects / git.git / blobdiff