Support 'diff=pgm' attribute

This enhances the attributes mechanism so that external programs
meant for existing GIT_EXTERNAL_DIFF interface can be specifed
per path.

To configure such a custom diff driver, first define a custom
diff driver in the configuration:

	[diff "my-c-diff"]
		command = <<your command string comes here>>

Then mark the paths that you want to use this custom driver
using the attribute mechanism.

	*.c	diff=my-c-diff

The intent of this separation is that the attribute mechanism is
used for specifying the type of the contents, while the
configuration mechanism is used to define what needs to be done
to that type of the contents, which would be specific to both
platform and personal taste.

Signed-off-by: Junio C Hamano <junkio@cox.net>

1 files changed, 97 insertions, 0 deletions

diff --git a/t/t4020-diff-external.sh b/t/t4020-diff-external.sh
new file mode 100755
index 0000000000..f0045cd788
--- /dev/null
+++ b/t/t4020-diff-external.sh
@@ -0,0 +1,97 @@
+#!/bin/sh
+
+test_description='external diff interface test'
+
+. ./test-lib.sh
+
+_z40=0000000000000000000000000000000000000000
+
+test_expect_success setup '
+
+	test_tick &&
+	echo initial >file &&
+	git add file &&
+	git commit -m initial &&
+
+	test_tick &&
+	echo second >file &&
+	git add file &&
+	git commit -m second &&
+
+	test_tick &&
+	echo third >file
+'
+
+test_expect_success 'GIT_EXTERNAL_DIFF environment' '
+
+	GIT_EXTERNAL_DIFF=echo git diff | {
+		read path oldfile oldhex oldmode newfile newhex newmode &&
+		test "z$path" = zfile &&
+		test "z$oldmode" = z100644 &&
+		test "z$newhex" = "z$_z40" &&
+		test "z$newmode" = z100644 &&
+		oh=$(git rev-parse --verify HEAD:file) &&
+		test "z$oh" = "z$oldhex"
+	}
+
+'
+
+test_expect_success 'GIT_EXTERNAL_DIFF environment should apply only to diff' '
+
+	GIT_EXTERNAL_DIFF=echo git log -p -1 HEAD |
+	grep "^diff --git a/file b/file"
+
+'
+
+test_expect_success 'diff attribute' '
+
+	git config diff.parrot.command echo &&
+
+	echo >.gitattributes "file diff=parrot" &&
+
+	git diff | {
+		read path oldfile oldhex oldmode newfile newhex newmode &&
+		test "z$path" = zfile &&
+		test "z$oldmode" = z100644 &&
+		test "z$newhex" = "z$_z40" &&
+		test "z$newmode" = z100644 &&
+		oh=$(git rev-parse --verify HEAD:file) &&
+		test "z$oh" = "z$oldhex"
+	}
+
+'
+
+test_expect_success 'diff attribute should apply only to diff' '
+
+	git log -p -1 HEAD |
+	grep "^diff --git a/file b/file"
+
+'
+
+test_expect_success 'diff attribute' '
+
+	git config --unset diff.parrot.command &&
+	git config diff.color.command echo &&
+
+	echo >.gitattributes "file diff=color" &&
+
+	git diff | {
+		read path oldfile oldhex oldmode newfile newhex newmode &&
+		test "z$path" = zfile &&
+		test "z$oldmode" = z100644 &&
+		test "z$newhex" = "z$_z40" &&
+		test "z$newmode" = z100644 &&
+		oh=$(git rev-parse --verify HEAD:file) &&
+		test "z$oh" = "z$oldhex"
+	}
+
+'
+
+test_expect_success 'diff attribute should apply only to diff' '
+
+	git log -p -1 HEAD |
+	grep "^diff --git a/file b/file"
+
+'
+
+test_done