* [PATCH 4/3] Finish making --emu23 equivalent to pure 2-way merge.
@ 2005-06-11 9:50 Junio C Hamano
0 siblings, 0 replies; only message in thread
From: Junio C Hamano @ 2005-06-11 9:50 UTC (permalink / raw)
To: Linus Torvalds; +Cc: git
This adds #3ALT rule (and #2ALT rule for symmetry) to the
read-tree 3-way merge logic that collapses paths that are added
only in one branch and not in the other internally.
This makes --emu23 to succeed in the last remaining case where
the pure 2-way merge succeeded and earlier one failed. Running
diff between t1001 and t1005 test scripts shows that the only
difference between the two is that --emu23 can leave the states
into separate stages so that the user can use usual 3-way merge
resolution techniques to carry forward the local changes when
pure 2-way merge would have refused to run.
Signed-off-by: Junio C Hamano <junkio@cox.net>
---
*** This is leftover bits from the earlier 3-piece series.
read-tree.c | 137 ++++++++++++++++++++++++++++++++++++-
t/t1000-read-tree-m-3way.sh | 32 +++++----
t/t1005-read-tree-m-2way-emu23.sh | 20 ++++-
3 files changed, 168 insertions(+), 21 deletions(-)
diff --git a/read-tree.c b/read-tree.c
--- a/read-tree.c
+++ b/read-tree.c
@@ -143,7 +143,72 @@ static int deleted_entry(struct cache_en
return 1;
}
-static int threeway_merge(struct cache_entry *stages[4], struct cache_entry **dst)
+static int causes_df_conflict(struct cache_entry *ce, int stage,
+ struct cache_entry **dst_,
+ struct cache_entry **next_,
+ int tail)
+{
+ /* This is called during the merge operation and walking
+ * the active_cache[] array is messy, because it is in the
+ * middle of overlapping copy operation. The invariants
+ * are:
+ * (1) active_cache points at the first (zeroth) entry.
+ * (2) up to dst pointer are resolved entries.
+ * (3) from the next pointer (head-inclusive) to the tail
+ * of the active_cache array have the remaining paths
+ * to be processed. There can be a gap between dst
+ * and next. Note that next is called "src" in the
+ * merge_cache() function, and tail is the original
+ * end of active_cache array when merge_cache() started.
+ * (4) the path corresponding to *ce is not found in (2)
+ * or (3). It is in the gap.
+ *
+ * active_cache -----......+++++++++++++.
+ * ^dst ^next ^tail
+ */
+ int i, next, dst;
+ const char *path = ce->name;
+ int namelen = ce_namelen(ce);
+
+ next = next_ - active_cache;
+ dst = dst_ - active_cache;
+
+ for (i = 0; i < tail; i++) {
+ int entlen, len;
+ const char *one, *two;
+ if (dst <= i && i < next)
+ continue;
+ ce = active_cache[i];
+ if (ce_stage(ce) != stage)
+ continue;
+ /* If ce->name is a prefix of path, then path is a file
+ * that hangs underneath ce->name, which is bad.
+ * If path is a prefix of ce->name, then it is the
+ * other way around which also is bad.
+ */
+ entlen = ce_namelen(ce);
+ if (namelen == entlen)
+ continue;
+ if (namelen < entlen) {
+ len = namelen;
+ one = path;
+ two = ce->name;
+ } else {
+ len = entlen;
+ one = ce->name;
+ two = path;
+ }
+ if (memcmp(one, two, len))
+ continue;
+ if (two[len] == '/')
+ return 1;
+ }
+ return 0;
+}
+
+static int threeway_merge(struct cache_entry *stages[4],
+ struct cache_entry **dst,
+ struct cache_entry **next, int tail)
{
struct cache_entry *old = stages[0];
struct cache_entry *a = stages[1], *b = stages[2], *c = stages[3];
@@ -156,6 +221,65 @@ static int threeway_merge(struct cache_e
return -1;
return merged_entry_allow_dirty(b, old, dst);
}
+ /* #2ALT and #3ALT */
+ if (!a && (!!b != !!c)) {
+ /*
+ * The reason we need to worry about directory/file
+ * conflicts only in #2ALT and #3ALT case is this:
+ *
+ * (1) For all other cases that read-tree internally
+ * resolves a path, we always have such a path in
+ * *both* stage2 and stage3 when we begin.
+ * Traditionally, the behaviour has been even
+ * stricter and we did not resolve a path without
+ * initially being in all of stage1, 2, and 3.
+ *
+ * (2) When read-tree finishes, all resolved paths (i.e.
+ * the paths that are in stage0) must have come from
+ * either stage2 or stage3. It is not possible to
+ * have a stage0 path as a result of a merge if
+ * neither stage2 nor stage3 had that path.
+ *
+ * (3) It is guaranteed that just after reading the
+ * stages, each stage cannot have directory/file
+ * conflicts on its own, because they are populated
+ * by reading hierarchy of a tree. Combined with
+ * (1) and (2) above, this means that no matter what
+ * combination of paths we take from stage2 and
+ * stage3 as a result of a merge, they cannot cause
+ * a directory/file conflict situation (otherwise
+ * the "guilty" path would have already had such a
+ * conflict in the original stage, either stage2
+ * or stage3). Although its stage2 is synthesized
+ * by overlaying the current index on top of "our
+ * head" tree, --emu23 case also has this guarantee,
+ * by calling add_cache_entry() to create such stage2
+ * entries.
+ *
+ * (4) Only #2ALT and #3ALT lack the guarantee (1).
+ * They resolve paths that exist only in stage2
+ * or stage3. The stage2 tree may have a file DF
+ * while stage3 tree may have a file DF/DF. If
+ * #2ALT and #3ALT rules happen to apply to both
+ * of them, we would end up having DF (coming from
+ * stage2) and DF/DF (from stage3) in the result.
+ * When we attempt to resolve a path that exists
+ * only in stage2, we need to make sure there is
+ * no path that would conflict with it in stage3
+ * and vice versa.
+ */
+ if (c) { /* #2ALT */
+ if (!causes_df_conflict(c, 2, dst, next, tail) &&
+ (!old || same(c, old)))
+ return merged_entry_allow_dirty(c, old, dst);
+ }
+ else { /* #3ALT */
+ if (!causes_df_conflict(b, 3, dst, next, tail) &&
+ (!old || same(b, old)))
+ return merged_entry_allow_dirty(b, old, dst);
+ }
+ /* otherwise we will apply the original rule */
+ }
/*
* If we have an entry in the index cache ("old"), then we want
* to make sure that it matches any entries in stage 2 ("first
@@ -186,7 +310,8 @@ static int threeway_merge(struct cache_e
* "carry forward" rule, please see <Documentation/git-read-tree.txt>.
*
*/
-static int twoway_merge(struct cache_entry **src, struct cache_entry **dst)
+static int twoway_merge(struct cache_entry **src, struct cache_entry **dst,
+ struct cache_entry **next, int tail)
{
struct cache_entry *current = src[0];
struct cache_entry *oldtree = src[1], *newtree = src[2];
@@ -283,7 +408,8 @@ static void setup_emu23(void)
* The rule is:
* - take the stat information from stage0, take the data from stage1
*/
-static int oneway_merge(struct cache_entry **src, struct cache_entry **dst)
+static int oneway_merge(struct cache_entry **src, struct cache_entry **dst,
+ struct cache_entry **next, int tail)
{
struct cache_entry *old = src[0];
struct cache_entry *a = src[1];
@@ -324,11 +450,12 @@ static void check_updates(struct cache_e
}
}
-typedef int (*merge_fn_t)(struct cache_entry **, struct cache_entry **);
+typedef int (*merge_fn_t)(struct cache_entry **, struct cache_entry **, struct cache_entry **, int);
static void merge_cache(struct cache_entry **src, int nr, merge_fn_t fn)
{
struct cache_entry **dst = src;
+ int tail = nr;
while (nr) {
int entries;
@@ -346,7 +473,7 @@ static void merge_cache(struct cache_ent
break;
}
- entries = fn(stages, dst);
+ entries = fn(stages, dst, src, tail);
if (entries < 0)
reject_merge(name);
dst += entries;
diff --git a/t/t1000-read-tree-m-3way.sh b/t/t1000-read-tree-m-3way.sh
--- a/t/t1000-read-tree-m-3way.sh
+++ b/t/t1000-read-tree-m-3way.sh
@@ -75,13 +75,13 @@ In addition:
. ../lib-read-tree-m-3way.sh
################################################################
-# Trivial "majority when 3 stages exist" merge plus #5ALT trivial
-# merge.
+# Trivial "majority when 3 stages exist" merge plus #2ALT, #3ALT
+# and #5ALT trivial merges.
cat >expected <<\EOF
100644 X 2 AA
100644 X 3 AA
-100644 X 2 AN
+100644 X 0 AN
100644 X 1 DD
100644 X 3 DF
100644 X 2 DF/DF
@@ -96,7 +96,7 @@ cat >expected <<\EOF
100644 X 2 MM
100644 X 3 MM
100644 X 0 MN
-100644 X 3 NA
+100644 X 0 NA
100644 X 1 ND
100644 X 2 ND
100644 X 0 NM
@@ -107,7 +107,7 @@ cat >expected <<\EOF
100644 X 3 TT
100644 X 2 Z/AA
100644 X 3 Z/AA
-100644 X 2 Z/AN
+100644 X 0 Z/AN
100644 X 1 Z/DD
100644 X 1 Z/DM
100644 X 3 Z/DM
@@ -119,7 +119,7 @@ cat >expected <<\EOF
100644 X 2 Z/MM
100644 X 3 Z/MM
100644 X 0 Z/MN
-100644 X 3 Z/NA
+100644 X 0 Z/NA
100644 X 1 Z/ND
100644 X 2 Z/ND
100644 X 0 Z/NM
@@ -233,23 +233,31 @@ test_expect_failure \
git-update-cache --add XX &&
git-read-tree -m $tree_O $tree_A $tree_B"
-test_expect_failure \
- '2 - must not have an entry not in A.' \
+test_expect_success \
+ '2 - must match B in !O && !A && B case.' \
+ "rm -f .git/index NA &&
+ cp .orig-B/NA NA &&
+ git-update-cache --add NA &&
+ git-read-tree -m $tree_O $tree_A $tree_B"
+
+test_expect_success \
+ '2 - matching B alone is OK in !O && !A && B case.' \
"rm -f .git/index NA &&
cp .orig-B/NA NA &&
git-update-cache --add NA &&
+ echo extra >>NA &&
git-read-tree -m $tree_O $tree_A $tree_B"
test_expect_success \
- '3 - must match and be up-to-date in !O && A && !B case.' \
+ '3 - must match A in !O && A && !B case.' \
"rm -f .git/index AN &&
cp .orig-A/AN AN &&
git-update-cache --add AN &&
git-read-tree -m $tree_O $tree_A $tree_B &&
check_result"
-test_expect_failure \
- '3 (fail) - must match and be up-to-date in !O && A && !B case.' \
+test_expect_success \
+ '3 - matching A alone is OK in !O && A && !B case.' \
"rm -f .git/index AN &&
cp .orig-A/AN AN &&
git-update-cache --add AN &&
@@ -257,7 +265,7 @@ test_expect_failure \
git-read-tree -m $tree_O $tree_A $tree_B"
test_expect_failure \
- '3 (fail) - must match and be up-to-date in !O && A && !B case.' \
+ '3 (fail) - must match A in !O && A && !B case.' \
"rm -f .git/index AN &&
cp .orig-A/AN AN &&
echo extra >>AN &&
diff --git a/t/t1005-read-tree-m-2way-emu23.sh b/t/t1005-read-tree-m-2way-emu23.sh
--- a/t/t1005-read-tree-m-2way-emu23.sh
+++ b/t/t1005-read-tree-m-2way-emu23.sh
@@ -80,6 +80,17 @@ test_expect_success \
git-ls-tree $treeM &&
git-diff-tree $treeH $treeM'
+# "read-tree -m H I+H M" but I is empty so this is "read-tree -m H H M".
+#
+# bozbar [O && A && B && O==A && O!=B (#14) ==> B] take M by read-tree
+# frotz [!O && !A && B (#2) ==> B] take M by read-tree
+# nitfol [O && A && B && O==A && O==B (#15) ==> B] take M by read-tree
+# rezrov [O && A && !B && O==A (#10) ==> no merge] removed by script
+#
+# Earlier one did not have #2ALT so taking M was done by the script,
+# which also updated the work tree and making frotz clean. With #2ALT,
+# this is resolved by read-tree itself and the path is left dirty
+# because we are not testing "read-tree -u --emu23".
test_expect_success \
'1, 2, 3 - no carry forward' \
'rm -f .git/index &&
@@ -87,7 +98,7 @@ test_expect_success \
git-ls-files --stage >1-3.out &&
diff -u M.out 1-3.out &&
check_cache_at bozbar dirty &&
- check_cache_at frotz clean && # different from pure 2-way
+ check_cache_at frotz dirty && # same as pure 2-way again.
check_cache_at nitfol dirty'
echo '+100644 X 0 yomin' >expected
@@ -103,8 +114,8 @@ test_expect_success \
check_cache_at yomin clean'
# "read-tree -m H I+H M" where !H && !M; so (I+H) not being up-to-date
-# should not matter, but without #3ALT this does not work.
-: test_expect_success \
+# should not matter. Thanks to #3ALT, this is now possible.
+test_expect_success \
'5 - carry forward local addition.' \
'rm -f .git/index &&
echo yomin >yomin &&
@@ -218,6 +229,7 @@ test_expect_success \
# This is different from straight 2-way merge in that it leaves
# three stages of bozbar in the index file without failing, so
# the user can run git-diff-stages to examine the situation.
+# With #2ALT, frotz is resolved internally.
test_expect_success \
'16 - conflicting local change.' \
'rm -f .git/index &&
@@ -228,7 +240,7 @@ test_expect_success \
100644 X 1 bozbar
100644 X 2 bozbar
100644 X 3 bozbar
-100644 X 3 frotz
+100644 X 0 frotz
100644 X 0 nitfol
100644 X 1 rezrov
100644 X 2 rezrov
------------
^ permalink raw reply [flat|nested] only message in thread
only message in thread, other threads:[~2005-06-11 9:47 UTC | newest]
Thread overview: (only message) (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2005-06-11 9:50 [PATCH 4/3] Finish making --emu23 equivalent to pure 2-way merge Junio C Hamano
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).