438195cced
This is the same as "-m", but it will silently ignore any unmerged entries, which makes it useful for efficiently forcing a new position regardless of the state of the current index file. IOW, to reset to a previous HEAD (in case you have had a failed merge, for example), you'd just do git-read-tree -u --reset HEAD which will also update your working tree to the right state. NOTE! The "update" will not remove files that may have been added by the merge. Yet.
369 lines
8.2 KiB
C
369 lines
8.2 KiB
C
/*
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* GIT - The information manager from hell
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*
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* Copyright (C) Linus Torvalds, 2005
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*/
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#include "cache.h"
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static int stage = 0;
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static int update = 0;
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static int unpack_tree(unsigned char *sha1)
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{
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void *buffer;
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unsigned long size;
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int ret;
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buffer = read_object_with_reference(sha1, "tree", &size, NULL);
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if (!buffer)
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return -1;
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ret = read_tree(buffer, size, stage);
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free(buffer);
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return ret;
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}
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static int path_matches(struct cache_entry *a, struct cache_entry *b)
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{
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int len = ce_namelen(a);
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return ce_namelen(b) == len &&
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!memcmp(a->name, b->name, len);
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}
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static int same(struct cache_entry *a, struct cache_entry *b)
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{
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return a->ce_mode == b->ce_mode &&
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!memcmp(a->sha1, b->sha1, 20);
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}
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/*
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* This removes all trivial merges that don't change the tree
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* and collapses them to state 0.
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*/
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static struct cache_entry *merge_entries(struct cache_entry *a,
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struct cache_entry *b,
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struct cache_entry *c)
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{
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/*
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* Ok, all three entries describe the same
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* filename, but maybe the contents or file
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* mode have changed?
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*
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* The trivial cases end up being the ones where two
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* out of three files are the same:
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* - both destinations the same, trivially take either
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* - one of the destination versions hasn't changed,
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* take the other.
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*
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* The "all entries exactly the same" case falls out as
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* a special case of any of the "two same" cases.
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*
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* Here "a" is "original", and "b" and "c" are the two
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* trees we are merging.
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*/
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if (a && b && c) {
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if (same(b,c))
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return c;
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if (same(a,b))
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return c;
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if (same(a,c))
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return b;
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}
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return NULL;
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}
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/*
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* When a CE gets turned into an unmerged entry, we
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* want it to be up-to-date
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*/
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static void verify_uptodate(struct cache_entry *ce)
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{
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struct stat st;
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if (!lstat(ce->name, &st)) {
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unsigned changed = ce_match_stat(ce, &st);
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if (!changed)
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return;
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errno = 0;
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}
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if (errno == ENOENT)
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return;
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die("Entry '%s' not uptodate. Cannot merge.", ce->name);
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}
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/*
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* If the old tree contained a CE that isn't even in the
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* result, that's always a problem, regardless of whether
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* it's up-to-date or not (ie it can be a file that we
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* have updated but not committed yet).
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*/
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static void reject_merge(struct cache_entry *ce)
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{
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die("Entry '%s' would be overwritten by merge. Cannot merge.", ce->name);
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}
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static int merged_entry(struct cache_entry *merge, struct cache_entry *old, struct cache_entry **dst)
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{
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merge->ce_flags |= htons(CE_UPDATE);
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if (old) {
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/*
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* See if we can re-use the old CE directly?
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* That way we get the uptodate stat info.
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*
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* This also removes the UPDATE flag on
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* a match.
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*/
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if (same(old, merge)) {
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*merge = *old;
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} else {
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verify_uptodate(old);
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}
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}
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merge->ce_flags &= ~htons(CE_STAGEMASK);
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*dst++ = merge;
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return 1;
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}
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static int threeway_merge(struct cache_entry *stages[4], struct cache_entry **dst)
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{
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struct cache_entry *old = stages[0];
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struct cache_entry *a = stages[1], *b = stages[2], *c = stages[3];
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struct cache_entry *merge;
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int count;
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/*
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* If we have an entry in the index cache ("old"), then we want
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* to make sure that it matches any entries in stage 2 ("first
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* branch", aka "b").
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*/
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if (old) {
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if (!b || !same(old, b))
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return -1;
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}
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merge = merge_entries(a, b, c);
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if (merge)
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return merged_entry(merge, old, dst);
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if (old)
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verify_uptodate(old);
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count = 0;
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if (a) { *dst++ = a; count++; }
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if (b) { *dst++ = b; count++; }
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if (c) { *dst++ = c; count++; }
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return count;
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}
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/*
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* Two-way merge.
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*
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* The rule is to "carry forward" what is in the index without losing
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* information across a "fast forward", favoring a successful merge
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* over a merge failure when it makes sense. For details of the
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* "carry forward" rule, please see <Documentation/git-read-tree.txt>.
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*
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*/
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static int twoway_merge(struct cache_entry **src, struct cache_entry **dst)
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{
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struct cache_entry *current = src[0];
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struct cache_entry *oldtree = src[1], *newtree = src[2];
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if (src[3])
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return -1;
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if (current) {
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if ((!oldtree && !newtree) || /* 4 and 5 */
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(!oldtree && newtree &&
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same(current, newtree)) || /* 6 and 7 */
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(oldtree && newtree &&
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same(oldtree, newtree)) || /* 14 and 15 */
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(oldtree && newtree &&
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!same(oldtree, newtree) && /* 18 and 19*/
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same(current, newtree))) {
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*dst++ = current;
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return 1;
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}
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else if (oldtree && !newtree && same(current, oldtree)) {
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/* 10 or 11 */
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verify_uptodate(current);
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return 0;
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}
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else if (oldtree && newtree &&
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same(current, oldtree) && !same(current, newtree)) {
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/* 20 or 21 */
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verify_uptodate(current);
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return merged_entry(newtree, NULL, dst);
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}
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else
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/* all other failures */
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return -1;
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}
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else if (newtree)
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return merged_entry(newtree, NULL, dst);
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else
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return 0;
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}
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/*
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* One-way merge.
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*
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* The rule is:
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* - take the stat information from stage0, take the data from stage1
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*/
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static int oneway_merge(struct cache_entry **src, struct cache_entry **dst)
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{
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struct cache_entry *old = src[0];
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struct cache_entry *a = src[1];
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if (src[2] || src[3])
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return -1;
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if (!a)
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return 0;
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if (old && same(old, a)) {
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*dst++ = old;
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return 1;
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}
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return merged_entry(a, NULL, dst);
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}
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static void check_updates(struct cache_entry **src, int nr)
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{
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static struct checkout state = {
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.base_dir = "",
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.force = 1,
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.quiet = 1,
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.refresh_cache = 1,
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};
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unsigned short mask = htons(CE_UPDATE);
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while (nr--) {
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struct cache_entry *ce = *src++;
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if (ce->ce_flags & mask) {
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ce->ce_flags &= ~mask;
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if (update)
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checkout_entry(ce, &state);
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}
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}
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}
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typedef int (*merge_fn_t)(struct cache_entry **, struct cache_entry **);
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static void merge_cache(struct cache_entry **src, int nr, merge_fn_t fn)
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{
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struct cache_entry **dst = src;
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while (nr) {
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int entries;
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struct cache_entry *name, *ce, *stages[4] = { NULL, };
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name = ce = *src;
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for (;;) {
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int stage = ce_stage(ce);
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stages[stage] = ce;
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ce = *++src;
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active_nr--;
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if (!--nr)
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break;
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if (!path_matches(ce, name))
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break;
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}
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entries = fn(stages, dst);
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if (entries < 0)
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reject_merge(name);
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dst += entries;
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active_nr += entries;
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}
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check_updates(active_cache, active_nr);
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}
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static int read_cache_unmerged(void)
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{
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int i, deleted;
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struct cache_entry **dst;
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read_cache();
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dst = active_cache;
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deleted = 0;
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for (i = 0; i < active_nr; i++) {
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struct cache_entry *ce = active_cache[i];
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if (ce_stage(ce)) {
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deleted++;
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continue;
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}
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if (deleted)
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*dst = ce;
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dst++;
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}
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active_nr -= deleted;
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return deleted;
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}
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static char *read_tree_usage = "git-read-tree (<sha> | -m [-u] <sha1> [<sha2> [<sha3>]])";
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static struct cache_file cache_file;
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int main(int argc, char **argv)
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{
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int i, newfd, merge, reset;
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unsigned char sha1[20];
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newfd = hold_index_file_for_update(&cache_file, get_index_file());
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if (newfd < 0)
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die("unable to create new cachefile");
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merge = 0;
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reset = 0;
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for (i = 1; i < argc; i++) {
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const char *arg = argv[i];
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/* "-u" means "update", meaning that a merge will update the working directory */
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if (!strcmp(arg, "-u")) {
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update = 1;
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continue;
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}
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/* This differs from "-m" in that we'll silently ignore unmerged entries */
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if (!strcmp(arg, "--reset")) {
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if (stage || merge)
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usage(read_tree_usage);
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reset = 1;
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merge = 1;
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stage = 1;
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read_cache_unmerged();
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}
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/* "-m" stands for "merge", meaning we start in stage 1 */
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if (!strcmp(arg, "-m")) {
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if (stage || merge)
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usage(read_tree_usage);
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if (read_cache_unmerged())
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die("you need to resolve your current index first");
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stage = 1;
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merge = 1;
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continue;
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}
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if (get_sha1(arg, sha1) < 0)
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usage(read_tree_usage);
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if (stage > 3)
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usage(read_tree_usage);
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if (unpack_tree(sha1) < 0)
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die("failed to unpack tree object %s", arg);
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stage++;
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}
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if (update && !merge)
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usage(read_tree_usage);
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if (merge) {
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static const merge_fn_t merge_function[] = {
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[1] = oneway_merge,
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[2] = twoway_merge,
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[3] = threeway_merge,
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};
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if (stage < 2 || stage > 4)
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die("just how do you expect me to merge %d trees?", stage-1);
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merge_cache(active_cache, active_nr, merge_function[stage-1]);
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}
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if (write_cache(newfd, active_cache, active_nr) ||
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commit_index_file(&cache_file))
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die("unable to write new index file");
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return 0;
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}
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