mirror of
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d925ffbd06
That's the final one ("Yeah, sure, we believe you").
Anyway, at least the tests pass, which is not saying a lot, since they
don't end up testing all the new the things that the new merge world
order tries to do. But hopefully we're now at least not any worse off
than we were before the rewrite.
384 lines
8.6 KiB
C
384 lines
8.6 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 char *lockfile_name;
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static void remove_lock_file(void)
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{
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if (lockfile_name)
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unlink(lockfile_name);
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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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* _Any_ other merge is left to user policy. That includes "both
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* created the same file", and "both removed the same file" - which are
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* trivial, but the user might still want to _note_ it.
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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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int len = ce_namelen(a);
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/*
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* Are they all the same filename? We won't do
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* any name merging
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*/
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if (ce_namelen(b) != len ||
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ce_namelen(c) != len ||
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memcmp(a->name, b->name, len) ||
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memcmp(a->name, c->name, len))
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return NULL;
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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 (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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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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#define CHECK_OLD(ce) if (old && same(old, ce)) { verify_uptodate(old); old = NULL; }
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static void trivially_merge_cache(struct cache_entry **src, int nr)
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{
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struct cache_entry **dst = src;
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struct cache_entry *old = NULL;
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while (nr--) {
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struct cache_entry *ce, *result;
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ce = *src++;
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/* We throw away original cache entries except for the stat information */
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if (!ce_stage(ce)) {
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if (old)
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reject_merge(old);
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old = ce;
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active_nr--;
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continue;
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}
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if (old && !path_matches(old, ce))
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reject_merge(old);
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if (nr > 1 && (result = merge_entries(ce, src[0], src[1])) != NULL) {
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result->ce_flags |= htons(CE_UPDATE);
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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 (old && same(old, result)) {
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*result = *old;
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old = NULL;
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}
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CHECK_OLD(ce);
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CHECK_OLD(src[0]);
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CHECK_OLD(src[1]);
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ce = result;
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ce->ce_flags &= ~htons(CE_STAGEMASK);
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src += 2;
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nr -= 2;
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active_nr -= 2;
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}
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/*
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* If we had an old entry that we now effectively
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* overwrite, make sure it wasn't dirty.
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*/
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CHECK_OLD(ce);
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*dst++ = ce;
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}
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if (old)
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reject_merge(old);
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}
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/*
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* When we find a "stage2" entry in the two-way merge, that's
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* the one that will remain. If we have an exact old match,
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* we don't care whether the file is up-to-date or not, we just
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* re-use the thing directly.
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*
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* If we didn't have an exact match, then we want to make sure
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* that we've seen a stage1 that matched the old, and that the
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* old file was up-to-date. Because it will be gone after this
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* merge..
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*/
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static void twoway_check(struct cache_entry *old, int seen_stage1, struct cache_entry *ce)
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{
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if (path_matches(old, ce)) {
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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, ce)) {
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*ce = *old;
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return;
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}
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if (!seen_stage1)
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reject_merge(old);
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}
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verify_uptodate(old);
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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:
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* - every current entry has to match the old tree
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* - if the current entry matches the new tree, we leave it
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* as-is. Otherwise we require that it be up-to-date.
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*/
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static void twoway_merge(struct cache_entry **src, int nr)
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{
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int seen_stage1 = 0;
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struct cache_entry *old = NULL;
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struct cache_entry **dst = src;
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while (nr--) {
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struct cache_entry *ce = *src++;
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int stage = ce_stage(ce);
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switch (stage) {
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case 0:
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if (old)
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reject_merge(old);
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old = ce;
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seen_stage1 = 0;
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active_nr--;
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continue;
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case 1:
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active_nr--;
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if (!old)
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continue;
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if (!path_matches(old, ce) || !same(old, ce))
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reject_merge(old);
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seen_stage1 = 1;
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continue;
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case 2:
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ce->ce_flags |= htons(CE_UPDATE);
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if (old) {
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twoway_check(old, seen_stage1, ce);
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old = NULL;
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}
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ce->ce_flags &= ~htons(CE_STAGEMASK);
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*dst++ = ce;
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continue;
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}
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die("impossible two-way stage");
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}
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/*
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* Unmatched with a new entry? Make sure it was
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* at least uptodate in the working directory _and_
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* the original tree..
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*/
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if (old) {
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if (!seen_stage1)
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reject_merge(old);
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verify_uptodate(old);
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}
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}
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static void merge_stat_info(struct cache_entry **src, int nr)
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{
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static struct cache_entry null_entry;
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struct cache_entry **dst = src;
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struct cache_entry *stat = &null_entry;
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while (nr--) {
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struct cache_entry *ce = *src++;
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/* We throw away original cache entries except for the stat information */
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if (!ce_stage(ce)) {
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stat = ce;
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active_nr--;
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continue;
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}
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if (path_matches(ce, stat) && same(ce, stat))
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*ce = *stat;
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ce->ce_flags &= ~htons(CE_STAGEMASK);
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*dst++ = ce;
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}
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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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static char *read_tree_usage = "git-read-tree (<sha> | -m <sha1> [<sha2> [<sha3>]])";
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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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static char lockfile[MAXPATHLEN+1];
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const char *indexfile = get_index_file();
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snprintf(lockfile, sizeof(lockfile), "%s.lock", indexfile);
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newfd = open(lockfile, O_RDWR | O_CREAT | O_EXCL, 0600);
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if (newfd < 0)
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die("unable to create new cachefile");
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atexit(remove_lock_file);
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lockfile_name = lockfile;
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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 (merge) {
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switch (stage) {
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case 4: /* Three-way merge */
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trivially_merge_cache(active_cache, active_nr);
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check_updates(active_cache, active_nr);
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break;
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case 3: /* Update from one tree to another */
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twoway_merge(active_cache, active_nr);
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check_updates(active_cache, active_nr);
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break;
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case 2: /* Just read a tree, merge with old cache contents */
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merge_stat_info(active_cache, active_nr);
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break;
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default:
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die("just how do you expect me to merge %d trees?", stage-1);
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}
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}
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if (write_cache(newfd, active_cache, active_nr) || rename(lockfile, indexfile))
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die("unable to write new index file");
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lockfile_name = NULL;
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return 0;
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}
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