revision.c: Make --full-history consider more merges

History simplification previously always treated merges as TREESAME
if they were TREESAME to any parent.

While this was consistent with the default behaviour, this could be
extremely unhelpful when searching detailed history, and could not be
overridden. For example, if a merge had ignored a change, as if by "-s
ours", then:

  git log -m -p --full-history -Schange file

would successfully locate "change"'s addition but would not locate the
merge that resolved against it.

Futher, simplify_merges could drop the actual parent that a commit
was TREESAME to, leaving it as a normal commit marked TREESAME that
isn't actually TREESAME to its remaining parent.

Now redefine a commit's TREESAME flag to be true only if a commit is
TREESAME to _all_ of its parents. This doesn't affect either the default
simplify_history behaviour (because partially TREESAME merges are turned
into normal commits), or full-history with parent rewriting (because all
merges are output). But it does affect other modes. The clearest
difference is that --full-history will show more merges - sufficient to
ensure that -m -p --full-history log searches can really explain every
change to the file, including those changes' ultimate fate in merges.

Also modify simplify_merges to recalculate TREESAME after removing
a parent. This is achieved by storing per-parent TREESAME flags on the
initial scan, so the combined flag can be easily recomputed.

This fixes some t6111 failures, but creates a couple of new ones -
we are now showing some merges that don't need to be shown.

Signed-off-by: Kevin Bracey <kevin@bracey.fi>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 13 insertions, 13 deletions

diff --git a/t/t6111-rev-list-treesame.sh b/t/t6111-rev-list-treesame.sh
index 4d74d3cfdf..0047b541fd 100755
--- a/t/t6111-rev-list-treesame.sh
+++ b/t/t6111-rev-list-treesame.sh
@@ -114,9 +114,9 @@ check_result '(LH)M (K)L (GJ)K (I)J (G)I (G)H (FE)G (D)F (B)E (BC)D (A)C (A)B A'
 check_result 'M H L K J I G E F D C B A' --topo-order
 check_result 'M L H B A' -- file
 check_result '(LH)M (B)L (B)H (A)B A' --parents -- file
-check_outcome failure 'M L J I H G F D B A' --full-history -- file # drops G
+check_result 'M L J I H G F D B A' --full-history -- file
 check_result '(LH)M (K)L (GJ)K (I)J (G)I (G)H (FB)G (D)F (BA)D (A)B A' --full-history --parents -- file
-check_outcome failure '(LH)M (G)H (J)L (I)J (G)I (FB)G (B)F (A)B A' --simplify-merges -- file # drops G
+check_outcome failure '(LH)M (G)H (J)L (I)J (G)I (FB)G (B)F (A)B A' --simplify-merges -- file # drops parent B from G
 check_result 'M L K G F D B A' --first-parent
 check_result 'M L G F B A' --first-parent -- file
 
@@ -125,11 +125,11 @@ check_result 'M L K J I H G E' F..M
 check_result 'M H L K J I G E' F..M --topo-order
 check_result 'M L H' F..M -- file
 check_result '(LH)M (B)L (B)H' --parents F..M -- file
-check_outcome failure 'M L J I H G' F..M --full-history -- file # drops G
+check_result 'M L J I H G' F..M --full-history -- file
 check_result '(LH)M (K)L (GJ)K (I)J (G)I (G)H (FB)G' F..M --full-history --parents -- file
-check_outcome failure '(LH)M (G)H (J)L (I)J (G)I (FB)G' F..M --simplify-merges -- file # drops G
+check_outcome failure '(LH)M (G)H (J)L (I)J (G)I (FB)G' F..M --simplify-merges -- file # drops parent B from G
 check_result 'M L K J I H G' F..M --ancestry-path
-check_outcome failure 'M L J I H G' F..M --ancestry-path -- file # drops G
+check_result 'M L J I H G' F..M --ancestry-path -- file
 check_result '(LH)M (K)L (GJ)K (I)J (G)I (G)H (FE)G' F..M --ancestry-path --parents -- file
 check_result '(LH)M (G)H (J)L (I)J (G)I (FE)G' F..M --ancestry-path --simplify-merges -- file
 check_result 'M L K G' F..M --first-parent
@@ -138,7 +138,7 @@ check_result 'M L G' F..M --first-parent -- file
 # Note that G is pruned when E is the bottom, even if it's the same commit list
 # If we want history since E, then we're quite happy to ignore G that took E.
 check_result 'M L K J I H G' E..M --ancestry-path
-check_result 'M L J I H' E..M --ancestry-path -- file
+check_outcome failure 'M L J I H' E..M --ancestry-path -- file # includes G
 check_outcome failure '(LH)M (K)L (EJ)K (I)J (E)I (E)H' E..M --ancestry-path --parents -- file # includes G
 check_outcome failure '(LH)M (E)H (J)L (I)J (E)I' E..M --ancestry-path --simplify-merges -- file # includes G
 
@@ -161,32 +161,32 @@ check_result 'M H L J I' G..M --ancestry-path --simplify-merges -- file
 # But --full-history shouldn't drop D on its own - without simplification,
 # we can't decide if the merge from INTERESTING commit C was sensible.
 check_result 'F D C' B..F
-check_result 'F' B..F -- file
+check_outcome failure 'F' B..F -- file # includes D
 check_outcome failure '(B)F' B..F --parents -- file # includes D
-check_outcome failure 'F D' B..F --full-history -- file # drops D prematurely
+check_result 'F D' B..F --full-history -- file
 check_result '(D)F (BA)D' B..F --full-history --parents -- file
 check_result '(B)F' B..F --simplify-merges -- file
 check_result 'F D' B..F --ancestry-path
-check_result 'F' B..F --ancestry-path -- file
+check_outcome failure 'F' B..F --ancestry-path -- file # includes D
 check_outcome failure 'F' B..F --ancestry-path --parents -- file # includes D
 check_outcome failure 'F' B..F --ancestry-path --simplify-merges -- file # includes D
 check_result 'F D' B..F --first-parent
 check_result 'F' B..F --first-parent -- file
 
 # E...F should be equivalent to E F ^B, and be able to drop D as above.
-check_result 'F' E F ^B -- file
-check_result 'F' E...F -- file
+check_outcome failure 'F' E F ^B -- file # includes D
+check_outcome failure 'F' E...F -- file # includes D
 
 # Any sort of full history of C..F should show D, as it's the connection to C,
 # and it differs from it.
 check_result 'F D B' C..F
 check_result 'F B' C..F -- file
 check_result '(B)F (A)B' C..F --parents -- file
-check_outcome failure 'F D B' C..F --full-history -- file # drops D
+check_result 'F D B' C..F --full-history -- file
 check_result '(D)F (BC)D (A)B' C..F --full-history --parents -- file
 check_result '(D)F (BC)D (A)B' C..F --simplify-merges -- file
 check_result 'F D' C..F --ancestry-path
-check_outcome failure 'F D' C..F --ancestry-path -- file # drops D
+check_result 'F D' C..F --ancestry-path -- file
 check_result 'F D' C..F --ancestry-path --parents -- file
 check_result 'F D' C..F --ancestry-path --simplify-merges -- file
 check_result 'F D B' C..F --first-parent