340 lines
7.6 KiB
C
340 lines
7.6 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 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;
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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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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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/* "-m" stands for "merge", meaning we start in stage 1 */
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if (!strcmp(arg, "-m")) {
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int i;
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if (stage)
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die("-m needs to come first");
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read_cache();
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for (i = 0; i < active_nr; i++) {
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if (ce_stage(active_cache[i]))
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die("you need to resolve your current index first");
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}
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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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