e7f9bc411c
This fixes too strong index requirement 3-way merge enforces in one case: the same file is added in both branches. In this case, the original code insisted that if the index file has that path, it must match our branch and be up-to-date. However in this particular case, it only has to match it, and can be dirty. We just need to make sure that we keep the work-tree copy instead of checking out the merge result. The resolution of such a path, however, cannot be left to outside script, because we will not keep the original stage0 entries for unmerged paths when read-tree finishes, and at that point, the knowledge of "if we resolve it to match the new file added in both branches, the merge succeeds and the work tree would not lose information, but we should _not_ update the work tree from the resulting index file" is lost. For this reason, the now code needs to resolve this case (#5ALT) internally. This affects some existing tests in the test suite, but all in positive ways. In t1000 (3-way test), this #5ALT case now gets one stage0 entry, instead of an identical stage2 and stage3 entry pair, for such a path, and one test that checked for merge failure (because the test assumed the "stricter-than-necessary" behaviour) does not have to fail anymore. In t1005 (emu23 test), two tests that involves a case where the work tree already had a change introduced in the upstream (aka "merged head"), the merge succeeds instead of failing. Signed-off-by: Junio C Hamano <junkio@cox.net> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
470 lines
11 KiB
C
470 lines
11 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_internal(struct cache_entry *merge, struct cache_entry *old, struct cache_entry **dst, int allow_dirty)
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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 if (!allow_dirty) {
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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 merged_entry_allow_dirty(struct cache_entry *merge, struct cache_entry *old, struct cache_entry **dst)
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{
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return merged_entry_internal(merge, old, dst, 1);
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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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return merged_entry_internal(merge, old, dst, 0);
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}
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static int deleted_entry(struct cache_entry *ce, struct cache_entry *old, struct cache_entry **dst)
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{
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if (old)
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verify_uptodate(old);
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ce->ce_mode = 0;
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*dst++ = ce;
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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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/* #5ALT */
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if (!a && b && c && same(b, c)) {
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if (old && !same(b, old))
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return -1;
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return merged_entry_allow_dirty(b, old, dst);
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}
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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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return deleted_entry(oldtree, current, dst);
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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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return merged_entry(newtree, current, 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, current, dst);
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else
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return deleted_entry(oldtree, current, dst);
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}
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/*
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* Two-way merge emulated with three-way merge.
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*
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* This treats "read-tree -m H M" by transforming it internally
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* into "read-tree -m H I+H M", where I+H is a tree that would
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* contain the contents of the current index file, overlayed on
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* top of H. Unlike the traditional two-way merge, this leaves
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* the stages in the resulting index file and lets the user resolve
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* the merge conflicts using standard tools for three-way merge.
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*
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* This function is just to set-up such an arrangement, and the
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* actual merge uses threeway_merge() function.
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*/
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static void setup_emu23(void)
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{
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/* stage0 contains I, stage1 H, stage2 M.
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* move stage2 to stage3, and create stage2 entries
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* by scanning stage0 and stage1 entries.
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*/
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int i, namelen, size;
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struct cache_entry *ce, *stage2;
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for (i = 0; i < active_nr; i++) {
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ce = active_cache[i];
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if (ce_stage(ce) != 2)
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continue;
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/* hoist them up to stage 3 */
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namelen = ce_namelen(ce);
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ce->ce_flags = create_ce_flags(namelen, 3);
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}
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for (i = 0; i < active_nr; i++) {
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ce = active_cache[i];
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if (ce_stage(ce) > 1)
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continue;
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namelen = ce_namelen(ce);
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size = cache_entry_size(namelen);
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stage2 = xmalloc(size);
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memcpy(stage2, ce, size);
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stage2->ce_flags = create_ce_flags(namelen, 2);
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if (add_cache_entry(stage2, ADD_CACHE_OK_TO_ADD) < 0)
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die("cannot merge index and our head tree");
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/* We are done with this name, so skip to next name */
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while (i < active_nr &&
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ce_namelen(active_cache[i]) == namelen &&
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!memcmp(active_cache[i]->name, ce->name, namelen))
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i++;
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i--; /* compensate for the loop control */
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}
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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_mode) {
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if (update)
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unlink(ce->name);
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continue;
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}
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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, emu23;
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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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emu23 = 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 || emu23)
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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 || emu23)
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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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/* "-emu23" uses 3-way merge logic to perform fast-forward */
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if (!strcmp(arg, "--emu23")) {
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if (stage || merge || emu23)
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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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merge = emu23 = stage = 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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merge_fn_t fn;
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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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if (emu23 && stage != 3)
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die("--emu23 takes only two trees");
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fn = merge_function[stage-1];
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if (stage == 3 && emu23) {
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setup_emu23();
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fn = merge_function[3];
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}
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merge_cache(active_cache, active_nr, fn);
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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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