*/
#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 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.
+ */
+static struct cache_entry *merge_entries(struct cache_entry *a,
+ struct cache_entry *b,
+ struct cache_entry *c)
+{
+ /*
+ * 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 (a && b && c) {
+ if (same(b,c))
+ return c;
+ if (same(a,b))
+ return c;
+ if (same(a,c))
+ return b;
}
- return 0;
+ 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;
+ }
+ 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);
+}
+
+static int merged_entry(struct cache_entry *merge, struct cache_entry *old, struct cache_entry **dst)
+{
+ merge->ce_flags |= htons(CE_UPDATE);
+ if (old) {
+ /*
+ * 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 (same(old, merge)) {
+ *merge = *old;
+ } else {
+ verify_uptodate(old);
+ }
+ }
+ merge->ce_flags &= ~htons(CE_STAGEMASK);
+ *dst++ = merge;
+ return 1;
+}
+
+static int threeway_merge(struct cache_entry *stages[4], struct cache_entry **dst)
+{
+ struct cache_entry *old = stages[0];
+ struct cache_entry *a = stages[1], *b = stages[2], *c = stages[3];
+ struct cache_entry *merge;
+ int count;
+
+ /*
+ * If we have an entry in the index cache ("old"), then we want
+ * to make sure that it matches any entries in stage 2 ("first
+ * branch", aka "b").
+ */
+ if (old) {
+ if (!b || !same(old, b))
+ return -1;
+ }
+ merge = merge_entries(a, b, c);
+ if (merge)
+ return merged_entry(merge, old, dst);
+ if (old)
+ verify_uptodate(old);
+ count = 0;
+ if (a) { *dst++ = a; count++; }
+ if (b) { *dst++ = b; count++; }
+ if (c) { *dst++ = c; count++; }
+ return count;
+}
+
+/*
+ * Two-way merge.
+ *
+ * The rule is to "carry forward" what is in the index without losing
+ * information across a "fast forward", favoring a successful merge
+ * over a merge failure when it makes sense. For details of the
+ * "carry forward" rule, please see <Documentation/git-read-tree.txt>.
+ *
+ */
+static int twoway_merge(struct cache_entry **src, struct cache_entry **dst)
+{
+ struct cache_entry *current = src[0];
+ struct cache_entry *oldtree = src[1], *newtree = src[2];
+
+ if (src[3])
+ return -1;
+
+ if (current) {
+ if ((!oldtree && !newtree) || /* 4 and 5 */
+ (!oldtree && newtree &&
+ same(current, newtree)) || /* 6 and 7 */
+ (oldtree && newtree &&
+ same(oldtree, newtree)) || /* 14 and 15 */
+ (oldtree && newtree &&
+ !same(oldtree, newtree) && /* 18 and 19*/
+ same(current, newtree))) {
+ *dst++ = current;
+ return 1;
+ }
+ else if (oldtree && !newtree && same(current, oldtree)) {
+ /* 10 or 11 */
+ verify_uptodate(current);
+ return 0;
+ }
+ else if (oldtree && newtree &&
+ same(current, oldtree) && !same(current, newtree)) {
+ /* 20 or 21 */
+ verify_uptodate(current);
+ return merged_entry(newtree, NULL, dst);
+ }
+ else
+ /* all other failures */
+ return -1;
+ }
+ else if (newtree)
+ return merged_entry(newtree, NULL, dst);
+ else
+ return 0;
+}
+
+/*
+ * One-way merge.
+ *
+ * The rule is:
+ * - take the stat information from stage0, take the data from stage1
+ */
+static int oneway_merge(struct cache_entry **src, struct cache_entry **dst)
+{
+ struct cache_entry *old = src[0];
+ struct cache_entry *a = src[1];
+
+ if (src[2] || src[3])
+ return -1;
+
+ if (!a)
+ return 0;
+ if (old && same(old, a)) {
+ *dst++ = old;
+ return 1;
+ }
+ return merged_entry(a, NULL, dst);
+}
+
+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);
+ }
+ }
+}
+
+typedef int (*merge_fn_t)(struct cache_entry **, struct cache_entry **);
+
+static void merge_cache(struct cache_entry **src, int nr, merge_fn_t fn)
+{
+ struct cache_entry **dst = src;
+
+ while (nr) {
+ int entries;
+ struct cache_entry *name, *ce, *stages[4] = { NULL, };
+
+ name = ce = *src;
+ for (;;) {
+ int stage = ce_stage(ce);
+ stages[stage] = ce;
+ ce = *++src;
+ active_nr--;
+ if (!--nr)
+ break;
+ if (!path_matches(ce, name))
+ break;
+ }
+
+ entries = fn(stages, dst);
+ if (entries < 0)
+ reject_merge(name);
+ dst += entries;
+ active_nr += entries;
+ }
+ check_updates(active_cache, active_nr);
+}
+
+static char *read_tree_usage = "git-read-tree (<sha> | -m [-u] <sha1> [<sha2> [<sha3>]])";
+
+static struct cache_file cache_file;
+
int main(int argc, char **argv)
{
- int fd;
+ int i, newfd, merge;
unsigned char sha1[20];
- 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");
+ newfd = hold_index_file_for_update(&cache_file, get_index_file());
+ if (newfd < 0)
+ die("unable to create new cachefile");
+
+ merge = 0;
+ for (i = 1; i < argc; i++) {
+ const char *arg = argv[i];
+
+ /* "-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 (update && !merge)
+ usage(read_tree_usage);
+ if (merge) {
+ static const merge_fn_t merge_function[] = {
+ [1] = oneway_merge,
+ [2] = twoway_merge,
+ [3] = threeway_merge,
+ };
+ if (stage < 2 || stage > 4)
+ die("just how do you expect me to merge %d trees?", stage-1);
+ merge_cache(active_cache, active_nr, merge_function[stage-1]);
+ }
+ if (write_cache(newfd, active_cache, active_nr) ||
+ commit_index_file(&cache_file))
+ die("unable to write new index file");
return 0;
}