range-diff: add tests

These are essentially lifted from https://github.com/trast/tbdiff, with
light touch-ups to account for the command now being named `git
range-diff`.

Apart from renaming `tbdiff` to `range-diff`, only one test case needed
to be adjusted: 11 - 'changed message'.

The underlying reason it had to be adjusted is that diff generation is
sometimes ambiguous. In this case, a comment line and an empty line are
added, but it is ambiguous whether they were added after the existing
empty line, or whether an empty line and the comment line are added
*before* the existing empty line. And apparently xdiff picks a different
option here than Python's difflib.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

3 files changed, 750 insertions, 0 deletions

diff --git a/t/.gitattributes b/t/.gitattributes
index 3bd959ae52..b17bf71b84 100644
--- a/t/.gitattributes
+++ b/t/.gitattributes
@@ -1,6 +1,7 @@
 t[0-9][0-9][0-9][0-9]/* -whitespace
 /diff-lib/* eol=lf
 /t0110/url-* binary
+/t3206/* eol=lf
 /t3900/*.txt eol=lf
 /t3901/*.txt eol=lf
 /t4034/*/* eol=lf
diff --git a/t/t3206-range-diff.sh b/t/t3206-range-diff.sh
new file mode 100755
index 0000000000..2237c7f4af
--- /dev/null
+++ b/t/t3206-range-diff.sh
@@ -0,0 +1,145 @@
+#!/bin/sh
+
+test_description='range-diff tests'
+
+. ./test-lib.sh
+
+# Note that because of the range-diff's heuristics, test_commit does more
+# harm than good.  We need some real history.
+
+test_expect_success 'setup' '
+	git fast-import < "$TEST_DIRECTORY"/t3206/history.export
+'
+
+test_expect_success 'simple A..B A..C (unmodified)' '
+	git range-diff --no-color master..topic master..unmodified \
+		>actual &&
+	cat >expected <<-EOF &&
+	1:  4de457d = 1:  35b9b25 s/5/A/
+	2:  fccce22 = 2:  de345ab s/4/A/
+	3:  147e64e = 3:  9af6654 s/11/B/
+	4:  a63e992 = 4:  2901f77 s/12/B/
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'simple B...C (unmodified)' '
+	git range-diff --no-color topic...unmodified >actual &&
+	# same "expected" as above
+	test_cmp expected actual
+'
+
+test_expect_success 'simple A B C (unmodified)' '
+	git range-diff --no-color master topic unmodified >actual &&
+	# same "expected" as above
+	test_cmp expected actual
+'
+
+test_expect_success 'trivial reordering' '
+	git range-diff --no-color master topic reordered >actual &&
+	cat >expected <<-EOF &&
+	1:  4de457d = 1:  aca177a s/5/A/
+	3:  147e64e = 2:  14ad629 s/11/B/
+	4:  a63e992 = 3:  ee58208 s/12/B/
+	2:  fccce22 = 4:  307b27a s/4/A/
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'removed a commit' '
+	git range-diff --no-color master topic removed >actual &&
+	cat >expected <<-EOF &&
+	1:  4de457d = 1:  7657159 s/5/A/
+	2:  fccce22 < -:  ------- s/4/A/
+	3:  147e64e = 2:  43d84d3 s/11/B/
+	4:  a63e992 = 3:  a740396 s/12/B/
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'added a commit' '
+	git range-diff --no-color master topic added >actual &&
+	cat >expected <<-EOF &&
+	1:  4de457d = 1:  2716022 s/5/A/
+	2:  fccce22 = 2:  b62accd s/4/A/
+	-:  ------- > 3:  df46cfa s/6/A/
+	3:  147e64e = 4:  3e64548 s/11/B/
+	4:  a63e992 = 5:  12b4063 s/12/B/
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'new base, A B C' '
+	git range-diff --no-color master topic rebased >actual &&
+	cat >expected <<-EOF &&
+	1:  4de457d = 1:  cc9c443 s/5/A/
+	2:  fccce22 = 2:  c5d9641 s/4/A/
+	3:  147e64e = 3:  28cc2b6 s/11/B/
+	4:  a63e992 = 4:  5628ab7 s/12/B/
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'new base, B...C' '
+	# this syntax includes the commits from master!
+	git range-diff --no-color topic...rebased >actual &&
+	cat >expected <<-EOF &&
+	-:  ------- > 1:  a31b12e unrelated
+	1:  4de457d = 2:  cc9c443 s/5/A/
+	2:  fccce22 = 3:  c5d9641 s/4/A/
+	3:  147e64e = 4:  28cc2b6 s/11/B/
+	4:  a63e992 = 5:  5628ab7 s/12/B/
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'changed commit' '
+	git range-diff --no-color topic...changed >actual &&
+	cat >expected <<-EOF &&
+	1:  4de457d = 1:  a4b3333 s/5/A/
+	2:  fccce22 = 2:  f51d370 s/4/A/
+	3:  147e64e ! 3:  0559556 s/11/B/
+	    @@ -10,7 +10,7 @@
+	      9
+	      10
+	     -11
+	    -+B
+	    ++BB
+	      12
+	      13
+	      14
+	4:  a63e992 ! 4:  d966c5c s/12/B/
+	    @@ -8,7 +8,7 @@
+	     @@
+	      9
+	      10
+	    - B
+	    + BB
+	     -12
+	     +B
+	      13
+	EOF
+	test_cmp expected actual
+'
+
+test_expect_success 'changed message' '
+	git range-diff --no-color topic...changed-message >actual &&
+	sed s/Z/\ /g >expected <<-EOF &&
+	1:  4de457d = 1:  f686024 s/5/A/
+	2:  fccce22 ! 2:  4ab067d s/4/A/
+	    @@ -2,6 +2,8 @@
+	    Z
+	    Z    s/4/A/
+	    Z
+	    +    Also a silly comment here!
+	    +
+	    Zdiff --git a/file b/file
+	    Z--- a/file
+	    Z+++ b/file
+	3:  147e64e = 3:  b9cb956 s/11/B/
+	4:  a63e992 = 4:  8add5f1 s/12/B/
+	EOF
+	test_cmp expected actual
+'
+
+test_done
diff --git a/t/t3206/history.export b/t/t3206/history.export
new file mode 100644
index 0000000000..b8ffff0940
--- /dev/null
+++ b/t/t3206/history.export
@@ -0,0 +1,604 @@
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