t6111: new TREESAME test set

Some side branching and odd merging to illustrate various flaws in
revision list scans, particularly when limiting the list.

Many expected failures, which will be gone by the end of the "history
traversal refinements" series.

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

t/t6111-rev-list-treesame.sh

@@ -0,0 +1,184 @@
+#!/bin/sh
+#
+#        ,---E--.   *H----------.             * marks !TREESAME parent paths
+#       /        \ /             \*
+# *A--*B---D--*F-*G---------K-*L-*M
+#   \     /*       \       /
+#    `-C-'          `-*I-*J
+#
+# A creates "file", B and F change it.
+# Odd merge G takes the old version from B.
+# I changes it, but J reverts it, so K is TREESAME to both parents.
+# H and L both change "file", and M merges those changes.
+
+test_description='TREESAME and limiting'
+
+. ./test-lib.sh
+
+note () {
+	git tag "$1"
+}
+
+unnote () {
+	git name-rev --tags --stdin | sed -e "s|$_x40 (tags/\([^)]*\)) |\1 |g"
+}
+
+test_expect_success setup '
+	test_commit "Initial file" file "Hi there" A &&
+	git branch other-branch &&
+
+	test_commit "file=Hello" file "Hello" B &&
+	git branch third-branch &&
+
+	git checkout other-branch &&
+	test_commit "Added other" other "Hello" C &&
+
+	git checkout master &&
+	test_merge D other-branch &&
+
+	git checkout third-branch &&
+	test_commit "Third file" third "Nothing" E &&
+
+	git checkout master &&
+	test_commit "file=Blah" file "Blah" F &&
+
+	test_tick && git merge --no-commit third-branch &&
+	git checkout third-branch file &&
+	git commit &&
+	note G &&
+	git branch fiddler-branch &&
+
+	git checkout -b part2-branch &&
+	test_commit "file=Part 2" file "Part 2" H &&
+
+	git checkout fiddler-branch &&
+	test_commit "Bad commit" file "Silly" I &&
+
+	test_tick && git revert I && note J &&
+
+	git checkout master &&
+	test_tick && git merge --no-ff fiddler-branch &&
+	note K
+
+	test_commit "file=Part 1" file "Part 1" L &&
+
+	test_tick && test_must_fail git merge part2-branch &&
+	test_commit M file "Parts 1+2"
+'
+
+FMT='tformat:%P 	%H | %s'
+
+# could we soup this up to optionally check parents? So "(BA)C" would check
+# that C is shown and has parents B A.
+check_outcome () {
+	outcome=$1
+	shift
+	for c in $1
+	do
+		echo "$c"
+	done >expect &&
+	shift &&
+	param="$*" &&
+	test_expect_$outcome "log $param" '
+		git log --format="$FMT" $param |
+		unnote >actual &&
+		sed -e "s/^.*	\([^ ]*\) .*/\1/" >check <actual &&
+		test_cmp expect check || {
+			cat actual
+			false
+		}
+	'
+}
+
+check_result () {
+	check_outcome success "$@"
+}
+
+# Odd merge G drops a change in F. Important that G is listed in all
+# except the most basic list. Achieving this means normal merge D will also be
+# shown in normal full-history, as we can't distinguish unless we do a
+# simplification pass. After simplification, D is dropped but G remains.
+check_result 'M L K J I H G F E D C 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 'M L H 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 K J I H G F D B A' --full-history --parents -- file
+check_outcome failure 'M H L J I G F B A' --simplify-merges -- file # drops G
+check_result 'M L K G F D B A' --first-parent
+check_result 'M L G F B A' --first-parent -- file
+
+# Check that odd merge G remains shown when F is the bottom.
+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 'M L H' F..M --parents -- file # L+H's parents rewritten to B, so more useful than it may seem
+check_outcome failure 'M L J I H G' F..M --full-history -- file # drops G
+check_result 'M L K J I H G' F..M --full-history --parents -- file
+check_outcome failure 'M H L J I G' F..M --simplify-merges -- file # drops 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 K J I H G' F..M --ancestry-path --parents -- file
+check_result 'M H L J I G' F..M --ancestry-path --simplify-merges -- file
+check_result 'M L K G' F..M --first-parent
+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 K J I H' E..M --ancestry-path --parents -- file # includes G
+check_outcome failure 'M H L J I' E..M --ancestry-path --simplify-merges -- file # includes G
+
+# Should still be able to ignore I-J branch in simple log, despite limiting
+# to G.
+check_result 'M L K J I H' G..M
+check_result 'M H L K J I' G..M --topo-order
+check_outcome failure 'M L H' G..M -- file # includes J I
+check_outcome failure 'M L H' G..M --parents -- file # includes J I
+check_result 'M L J I H' G..M --full-history -- file
+check_result 'M L K J I H' G..M --full-history --parents -- file
+check_result 'M H L J I' G..M --simplify-merges -- file
+check_result 'M L K J I H' G..M --ancestry-path
+check_result 'M L J I H' G..M --ancestry-path -- file
+check_result 'M L K J I H' G..M --ancestry-path --parents -- file
+check_result 'M H L J I' G..M --ancestry-path --simplify-merges -- file
+
+# B..F should be able to simplify the merge D from irrelevant side branch C.
+# Default log should also be free to follow B-D, and ignore C.
+# 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 --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 --parents -- file
+check_result '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 --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
+
+# 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 'F 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 --parents -- file
+check_result 'F D 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 --parents -- file
+check_result 'F D' C..F --ancestry-path --simplify-merges -- file
+check_result 'F D B' C..F --first-parent
+check_result 'F B' C..F --first-parent -- file
+
+
+test_done