0ca14a57f1
The same way "git-diff-tree" can limit its output to just a set of matches, we can read in just a partial tree for comparison purposes.
604 lines
16 KiB
C
604 lines
16 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, NULL);
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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 causes_df_conflict(struct cache_entry *ce, int stage,
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struct cache_entry **dst_,
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struct cache_entry **next_,
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int tail)
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{
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/* This is called during the merge operation and walking
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* the active_cache[] array is messy, because it is in the
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* middle of overlapping copy operation. The invariants
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* are:
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* (1) active_cache points at the first (zeroth) entry.
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* (2) up to dst pointer are resolved entries.
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* (3) from the next pointer (head-inclusive) to the tail
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* of the active_cache array have the remaining paths
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* to be processed. There can be a gap between dst
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* and next. Note that next is called "src" in the
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* merge_cache() function, and tail is the original
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* end of active_cache array when merge_cache() started.
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* (4) the path corresponding to *ce is not found in (2)
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* or (3). It is in the gap.
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*
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* active_cache -----......+++++++++++++.
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* ^dst ^next ^tail
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*/
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int i, next, dst;
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const char *path = ce->name;
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int namelen = ce_namelen(ce);
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next = next_ - active_cache;
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dst = dst_ - active_cache;
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for (i = 0; i < tail; i++) {
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int entlen, len;
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const char *one, *two;
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if (dst <= i && i < next)
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continue;
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ce = active_cache[i];
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if (ce_stage(ce) != stage)
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continue;
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/* If ce->name is a prefix of path, then path is a file
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* that hangs underneath ce->name, which is bad.
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* If path is a prefix of ce->name, then it is the
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* other way around which also is bad.
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*/
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entlen = ce_namelen(ce);
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if (namelen == entlen)
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continue;
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if (namelen < entlen) {
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len = namelen;
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one = path;
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two = ce->name;
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} else {
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len = entlen;
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one = ce->name;
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two = path;
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}
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if (memcmp(one, two, len))
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continue;
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if (two[len] == '/')
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return 1;
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}
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return 0;
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}
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static int threeway_merge(struct cache_entry *stages[4],
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struct cache_entry **dst,
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struct cache_entry **next, int tail)
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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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/* #2ALT and #3ALT */
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if (!a && (!!b != !!c)) {
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/*
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* The reason we need to worry about directory/file
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* conflicts only in #2ALT and #3ALT case is this:
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*
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* (1) For all other cases that read-tree internally
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* resolves a path, we always have such a path in
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* *both* stage2 and stage3 when we begin.
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* Traditionally, the behaviour has been even
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* stricter and we did not resolve a path without
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* initially being in all of stage1, 2, and 3.
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*
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* (2) When read-tree finishes, all resolved paths (i.e.
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* the paths that are in stage0) must have come from
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* either stage2 or stage3. It is not possible to
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* have a stage0 path as a result of a merge if
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* neither stage2 nor stage3 had that path.
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*
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* (3) It is guaranteed that just after reading the
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* stages, each stage cannot have directory/file
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* conflicts on its own, because they are populated
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* by reading hierarchy of a tree. Combined with
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* (1) and (2) above, this means that no matter what
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* combination of paths we take from stage2 and
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* stage3 as a result of a merge, they cannot cause
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* a directory/file conflict situation (otherwise
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* the "guilty" path would have already had such a
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* conflict in the original stage, either stage2
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* or stage3). Although its stage2 is synthesized
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* by overlaying the current index on top of "our
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* head" tree, --emu23 case also has this guarantee,
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* by calling add_cache_entry() to create such stage2
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* entries.
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*
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* (4) Only #2ALT and #3ALT lack the guarantee (1).
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* They resolve paths that exist only in stage2
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* or stage3. The stage2 tree may have a file DF
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* while stage3 tree may have a file DF/DF. If
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* #2ALT and #3ALT rules happen to apply to both
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* of them, we would end up having DF (coming from
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* stage2) and DF/DF (from stage3) in the result.
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* When we attempt to resolve a path that exists
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* only in stage2, we need to make sure there is
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* no path that would conflict with it in stage3
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* and vice versa.
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*/
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if (c) { /* #2ALT */
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if (!causes_df_conflict(c, 2, dst, next, tail) &&
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(!old || same(c, old)))
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return merged_entry_allow_dirty(c, old, dst);
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}
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else { /* #3ALT */
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if (!causes_df_conflict(b, 3, dst, next, tail) &&
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(!old || same(b, old)))
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return merged_entry_allow_dirty(b, old, dst);
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}
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/* otherwise we will apply the original rule */
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}
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/* #14ALT */
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if (a && b && c && same(a, b) && !same(a, c)) {
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if (old && same(old, c))
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return merged_entry_allow_dirty(c, old, dst);
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/* otherwise the regular rule applies */
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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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struct cache_entry **next, int tail)
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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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struct cache_entry **next, int tail)
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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 **, struct cache_entry **, int);
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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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int tail = nr;
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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, src, tail);
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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];
|
|
|
|
/* "-u" means "update", meaning that a merge will update the working directory */
|
|
if (!strcmp(arg, "-u")) {
|
|
update = 1;
|
|
continue;
|
|
}
|
|
|
|
/* This differs from "-m" in that we'll silently ignore unmerged entries */
|
|
if (!strcmp(arg, "--reset")) {
|
|
if (stage || merge || emu23)
|
|
usage(read_tree_usage);
|
|
reset = 1;
|
|
merge = 1;
|
|
stage = 1;
|
|
read_cache_unmerged();
|
|
continue;
|
|
}
|
|
|
|
/* "-m" stands for "merge", meaning we start in stage 1 */
|
|
if (!strcmp(arg, "-m")) {
|
|
if (stage || merge || emu23)
|
|
usage(read_tree_usage);
|
|
if (read_cache_unmerged())
|
|
die("you need to resolve your current index first");
|
|
stage = 1;
|
|
merge = 1;
|
|
continue;
|
|
}
|
|
|
|
/* "-emu23" uses 3-way merge logic to perform fast-forward */
|
|
if (!strcmp(arg, "--emu23")) {
|
|
if (stage || merge || emu23)
|
|
usage(read_tree_usage);
|
|
if (read_cache_unmerged())
|
|
die("you need to resolve your current index first");
|
|
merge = emu23 = stage = 1;
|
|
continue;
|
|
}
|
|
|
|
if (get_sha1(arg, sha1) < 0)
|
|
usage(read_tree_usage);
|
|
if (stage > 3)
|
|
usage(read_tree_usage);
|
|
if (unpack_tree(sha1) < 0)
|
|
die("failed to unpack tree object %s", arg);
|
|
stage++;
|
|
}
|
|
if (update && !merge)
|
|
usage(read_tree_usage);
|
|
if (merge) {
|
|
static const merge_fn_t merge_function[] = {
|
|
[1] = oneway_merge,
|
|
[2] = twoway_merge,
|
|
[3] = threeway_merge,
|
|
};
|
|
merge_fn_t fn;
|
|
|
|
if (stage < 2 || stage > 4)
|
|
die("just how do you expect me to merge %d trees?", stage-1);
|
|
if (emu23 && stage != 3)
|
|
die("--emu23 takes only two trees");
|
|
fn = merge_function[stage-1];
|
|
if (stage == 3 && emu23) {
|
|
setup_emu23();
|
|
fn = merge_function[3];
|
|
}
|
|
merge_cache(active_cache, active_nr, fn);
|
|
}
|
|
if (write_cache(newfd, active_cache, active_nr) ||
|
|
commit_index_file(&cache_file))
|
|
die("unable to write new index file");
|
|
return 0;
|
|
}
|