diff.c: decouple white space treatment from move detection algorithm

In the original implementation of the move detection logic the choice for
ignoring white space changes is the same for the move detection as it is
for the regular diff.  Some cases came up where different treatment would
have been nice.

Allow the user to specify that white space should be ignored differently
during detection of moved lines than during generation of added and removed
lines. This is done by providing analogs to the --ignore-space-at-eol,
-b, and -w options by introducing the option --color-moved-ws=<modes>
with the modes named "ignore-space-at-eol", "ignore-space-change" and
"ignore-all-space", which is used only during the move detection phase.

As we change the default, we'll adjust the tests.

For now we do not infer any options to treat white spaces in the move
detection from the generic white space options given to diff.
This can be tuned later to reasonable default.

As we plan on adding more white space related options in a later patch,
that interferes with the current white space options, use a flag field
and clamp it down to  XDF_WHITESPACE_FLAGS, as that (a) allows to easily
check at parse time if we give invalid combinations and (b) can reuse
parts of this patch.

By having the white space treatment in its own option, we'll also
make it easier for a later patch to have an config option for
spaces in the move detection.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 58 insertions, 4 deletions

diff --git a/t/t4015-diff-whitespace.sh b/t/t4015-diff-whitespace.sh
index e54529f026..000c3a2b7d 100755
--- a/t/t4015-diff-whitespace.sh
+++ b/t/t4015-diff-whitespace.sh
@@ -1460,7 +1460,8 @@ test_expect_success 'move detection ignoring whitespace ' '
 	EOF
 	test_cmp expected actual &&
 
-	git diff HEAD --no-renames -w --color-moved --color >actual.raw &&
+	git diff HEAD --no-renames --color-moved --color \
+		--color-moved-ws=ignore-all-space >actual.raw &&
 	grep -v "index" actual.raw | test_decode_color >actual &&
 	cat <<-\EOF >expected &&
 	<BOLD>diff --git a/lines.txt b/lines.txt<RESET>
@@ -1522,7 +1523,8 @@ test_expect_success 'move detection ignoring whitespace changes' '
 	EOF
 	test_cmp expected actual &&
 
-	git diff HEAD --no-renames -b --color-moved --color >actual.raw &&
+	git diff HEAD --no-renames --color-moved --color \
+		--color-moved-ws=ignore-space-change >actual.raw &&
 	grep -v "index" actual.raw | test_decode_color >actual &&
 	cat <<-\EOF >expected &&
 	<BOLD>diff --git a/lines.txt b/lines.txt<RESET>
@@ -1587,7 +1589,8 @@ test_expect_success 'move detection ignoring whitespace at eol' '
 	EOF
 	test_cmp expected actual &&
 
-	git diff HEAD --no-renames --ignore-space-at-eol --color-moved --color >actual.raw &&
+	git diff HEAD --no-renames --color-moved --color \
+		--color-moved-ws=ignore-space-at-eol >actual.raw &&
 	grep -v "index" actual.raw | test_decode_color >actual &&
 	cat <<-\EOF >expected &&
 	<BOLD>diff --git a/lines.txt b/lines.txt<RESET>
@@ -1757,7 +1760,58 @@ test_expect_success 'move detection with submodules' '
 
 	# nor did we mess with it another way
 	git diff --submodule=diff --color | test_decode_color >expect &&
-	test_cmp expect decoded_actual
+	test_cmp expect decoded_actual &&
+	rm -rf bananas &&
+	git submodule deinit bananas
+'
+
+test_expect_success 'only move detection ignores white spaces' '
+	git reset --hard &&
+	q_to_tab <<-\EOF >text.txt &&
+		a long line to exceed per-line minimum
+		another long line to exceed per-line minimum
+		original file
+	EOF
+	git add text.txt &&
+	git commit -m "add text" &&
+	q_to_tab <<-\EOF >text.txt &&
+		Qa long line to exceed per-line minimum
+		Qanother long line to exceed per-line minimum
+		new file
+	EOF
+
+	# Make sure we get a different diff using -w
+	git diff --color --color-moved -w >actual.raw &&
+	grep -v "index" actual.raw | test_decode_color >actual &&
+	q_to_tab <<-\EOF >expected &&
+	<BOLD>diff --git a/text.txt b/text.txt<RESET>
+	<BOLD>--- a/text.txt<RESET>
+	<BOLD>+++ b/text.txt<RESET>
+	<CYAN>@@ -1,3 +1,3 @@<RESET>
+	 Qa long line to exceed per-line minimum<RESET>
+	 Qanother long line to exceed per-line minimum<RESET>
+	<RED>-original file<RESET>
+	<GREEN>+<RESET><GREEN>new file<RESET>
+	EOF
+	test_cmp expected actual &&
+
+	# And now ignoring white space only in the move detection
+	git diff --color --color-moved \
+		--color-moved-ws=ignore-all-space,ignore-space-change,ignore-space-at-eol >actual.raw &&
+	grep -v "index" actual.raw | test_decode_color >actual &&
+	q_to_tab <<-\EOF >expected &&
+	<BOLD>diff --git a/text.txt b/text.txt<RESET>
+	<BOLD>--- a/text.txt<RESET>
+	<BOLD>+++ b/text.txt<RESET>
+	<CYAN>@@ -1,3 +1,3 @@<RESET>
+	<BOLD;MAGENTA>-a long line to exceed per-line minimum<RESET>
+	<BOLD;MAGENTA>-another long line to exceed per-line minimum<RESET>
+	<RED>-original file<RESET>
+	<BOLD;YELLOW>+<RESET>Q<BOLD;YELLOW>a long line to exceed per-line minimum<RESET>
+	<BOLD;YELLOW>+<RESET>Q<BOLD;YELLOW>another long line to exceed per-line minimum<RESET>
+	<GREEN>+<RESET><GREEN>new file<RESET>
+	EOF
+	test_cmp expected actual
 '
 
 test_done