graph: add support for --line-prefix on all graph-aware output

Add an extension to git-diff and git-log (and any other graph-aware
displayable output) such that "--line-prefix=<string>" will print the
additional line-prefix on every line of output.

To make this work, we have to fix a few bugs in the graph API that force
graph_show_commit_msg to be used only when you have a valid graph.
Additionally, we extend the default_diff_output_prefix handler to work
even when no graph is enabled.

This is somewhat of a hack on top of the graph API, but I think it
should be acceptable here.

This will be used by a future extension of submodule display which
displays the submodule diff as the actual diff between the pre and post
commit in the submodule project.

Add some tests for both git-log and git-diff to ensure that the prefix
is honored correctly.

Signed-off-by: Jacob Keller <jacob.keller@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

4 files changed, 373 insertions, 0 deletions

diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
index 94ef5000e7..566817e2ef 100755
--- a/t/t4013-diff-various.sh
+++ b/t/t4013-diff-various.sh
@@ -306,6 +306,8 @@ diff --no-index --name-status dir2 dir
 diff --no-index --name-status -- dir2 dir
 diff --no-index dir dir3
 diff master master^ side
+# Can't use spaces...
+diff --line-prefix=abc master master^ side
 diff --dirstat master~1 master~2
 diff --dirstat initial rearrange
 diff --dirstat-by-file initial rearrange
@@ -325,6 +327,10 @@ test_expect_success 'diff --cached -- file on unborn branch' '
 	git diff --cached -- file0 >result &&
 	test_cmp "$TEST_DIRECTORY/t4013/diff.diff_--cached_--_file0" result
 '
+test_expect_success 'diff --line-prefix with spaces' '
+	git diff --line-prefix="| | | " --cached -- file0 >result &&
+	test_cmp "$TEST_DIRECTORY/t4013/diff.diff_--line-prefix_--cached_--_file0" result
+'
 
 test_expect_success 'diff-tree --stdin with log formatting' '
 	cat >expect <<-\EOF &&
diff --git a/t/t4013/diff.diff_--line-prefix=abc_master_master^_side b/t/t4013/diff.diff_--line-prefix=abc_master_master^_side
new file mode 100644
index 0000000000..99f91e7f0e
--- /dev/null
+++ b/t/t4013/diff.diff_--line-prefix=abc_master_master^_side
@@ -0,0 +1,29 @@
+$ git diff --line-prefix=abc master master^ side
+abcdiff --cc dir/sub
+abcindex cead32e,7289e35..992913c
+abc--- a/dir/sub
+abc+++ b/dir/sub
+abc@@@ -1,6 -1,4 +1,8 @@@
+abc  A
+abc  B
+abc +C
+abc +D
+abc +E
+abc +F
+abc+ 1
+abc+ 2
+abcdiff --cc file0
+abcindex b414108,f4615da..10a8a9f
+abc--- a/file0
+abc+++ b/file0
+abc@@@ -1,6 -1,6 +1,9 @@@
+abc  1
+abc  2
+abc  3
+abc +4
+abc +5
+abc +6
+abc+ A
+abc+ B
+abc+ C
+$
diff --git a/t/t4013/diff.diff_--line-prefix_--cached_--_file0 b/t/t4013/diff.diff_--line-prefix_--cached_--_file0
new file mode 100644
index 0000000000..f41ba4d36a
--- /dev/null
+++ b/t/t4013/diff.diff_--line-prefix_--cached_--_file0
@@ -0,0 +1,15 @@
+| | | diff --git a/file0 b/file0
+| | | new file mode 100644
+| | | index 0000000..10a8a9f
+| | | --- /dev/null
+| | | +++ b/file0
+| | | @@ -0,0 +1,9 @@
+| | | +1
+| | | +2
+| | | +3
+| | | +4
+| | | +5
+| | | +6
+| | | +A
+| | | +B
+| | | +C
diff --git a/t/t4202-log.sh b/t/t4202-log.sh
index e2db47c36e..1ccbd5948a 100755
--- a/t/t4202-log.sh
+++ b/t/t4202-log.sh
@@ -188,6 +188,16 @@ test_expect_success 'git log --no-walk=sorted <commits> sorts by commit time' '
 '
 
 cat > expect << EOF
+=== 804a787 sixth
+=== 394ef78 fifth
+=== 5d31159 fourth
+EOF
+test_expect_success 'git log --line-prefix="=== " --no-walk <commits> sorts by commit time' '
+	git log --line-prefix="=== " --no-walk --oneline 5d31159 804a787 394ef78 > actual &&
+	test_cmp expect actual
+'
+
+cat > expect << EOF
 5d31159 fourth
 804a787 sixth
 394ef78 fifth
@@ -284,6 +294,21 @@ test_expect_success 'simple log --graph' '
 	test_cmp expect actual
 '
 
+cat > expect <<EOF
+123 * Second
+123 * sixth
+123 * fifth
+123 * fourth
+123 * third
+123 * second
+123 * initial
+EOF
+
+test_expect_success 'simple log --graph --line-prefix="123 "' '
+	git log --graph --line-prefix="123 " --pretty=tformat:%s >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'set up merge history' '
 	git checkout -b side HEAD~4 &&
 	test_commit side-1 1 1 &&
@@ -313,6 +338,27 @@ test_expect_success 'log --graph with merge' '
 	test_cmp expect actual
 '
 
+cat > expect <<\EOF
+| | | *   Merge branch 'side'
+| | | |\
+| | | | * side-2
+| | | | * side-1
+| | | * | Second
+| | | * | sixth
+| | | * | fifth
+| | | * | fourth
+| | | |/
+| | | * third
+| | | * second
+| | | * initial
+EOF
+
+test_expect_success 'log --graph --line-prefix="| | | " with merge' '
+	git log --line-prefix="| | | " --graph --date-order --pretty=tformat:%s |
+		sed "s/ *\$//" >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'log --raw --graph -m with merge' '
 	git log --raw --graph --oneline -m master | head -n 500 >actual &&
 	grep "initial" actual
@@ -867,6 +913,283 @@ test_expect_success 'log --graph with diff and stats' '
 	test_i18ncmp expect actual.sanitized
 '
 
+cat >expect <<\EOF
+*** *   commit COMMIT_OBJECT_NAME
+*** |\  Merge: MERGE_PARENTS
+*** | | Author: A U Thor <author@example.com>
+*** | |
+*** | |     Merge HEADS DESCRIPTION
+*** | |
+*** | * commit COMMIT_OBJECT_NAME
+*** | | Author: A U Thor <author@example.com>
+*** | |
+*** | |     reach
+*** | | ---
+*** | |  reach.t | 1 +
+*** | |  1 file changed, 1 insertion(+)
+*** | |
+*** | | diff --git a/reach.t b/reach.t
+*** | | new file mode 100644
+*** | | index 0000000..10c9591
+*** | | --- /dev/null
+*** | | +++ b/reach.t
+*** | | @@ -0,0 +1 @@
+*** | | +reach
+*** | |
+*** |  \
+*** *-. \   commit COMMIT_OBJECT_NAME
+*** |\ \ \  Merge: MERGE_PARENTS
+*** | | | | Author: A U Thor <author@example.com>
+*** | | | |
+*** | | | |     Merge HEADS DESCRIPTION
+*** | | | |
+*** | | * | commit COMMIT_OBJECT_NAME
+*** | | |/  Author: A U Thor <author@example.com>
+*** | | |
+*** | | |       octopus-b
+*** | | |   ---
+*** | | |    octopus-b.t | 1 +
+*** | | |    1 file changed, 1 insertion(+)
+*** | | |
+*** | | |   diff --git a/octopus-b.t b/octopus-b.t
+*** | | |   new file mode 100644
+*** | | |   index 0000000..d5fcad0
+*** | | |   --- /dev/null
+*** | | |   +++ b/octopus-b.t
+*** | | |   @@ -0,0 +1 @@
+*** | | |   +octopus-b
+*** | | |
+*** | * | commit COMMIT_OBJECT_NAME
+*** | |/  Author: A U Thor <author@example.com>
+*** | |
+*** | |       octopus-a
+*** | |   ---
+*** | |    octopus-a.t | 1 +
+*** | |    1 file changed, 1 insertion(+)
+*** | |
+*** | |   diff --git a/octopus-a.t b/octopus-a.t
+*** | |   new file mode 100644
+*** | |   index 0000000..11ee015
+*** | |   --- /dev/null
+*** | |   +++ b/octopus-a.t
+*** | |   @@ -0,0 +1 @@
+*** | |   +octopus-a
+*** | |
+*** * | commit COMMIT_OBJECT_NAME
+*** |/  Author: A U Thor <author@example.com>
+*** |
+*** |       seventh
+*** |   ---
+*** |    seventh.t | 1 +
+*** |    1 file changed, 1 insertion(+)
+*** |
+*** |   diff --git a/seventh.t b/seventh.t
+*** |   new file mode 100644
+*** |   index 0000000..9744ffc
+*** |   --- /dev/null
+*** |   +++ b/seventh.t
+*** |   @@ -0,0 +1 @@
+*** |   +seventh
+*** |
+*** *   commit COMMIT_OBJECT_NAME
+*** |\  Merge: MERGE_PARENTS
+*** | | Author: A U Thor <author@example.com>
+*** | |
+*** | |     Merge branch 'tangle'
+*** | |
+*** | *   commit COMMIT_OBJECT_NAME
+*** | |\  Merge: MERGE_PARENTS
+*** | | | Author: A U Thor <author@example.com>
+*** | | |
+*** | | |     Merge branch 'side' (early part) into tangle
+*** | | |
+*** | * |   commit COMMIT_OBJECT_NAME
+*** | |\ \  Merge: MERGE_PARENTS
+*** | | | | Author: A U Thor <author@example.com>
+*** | | | |
+*** | | | |     Merge branch 'master' (early part) into tangle
+*** | | | |
+*** | * | | commit COMMIT_OBJECT_NAME
+*** | | | | Author: A U Thor <author@example.com>
+*** | | | |
+*** | | | |     tangle-a
+*** | | | | ---
+*** | | | |  tangle-a | 1 +
+*** | | | |  1 file changed, 1 insertion(+)
+*** | | | |
+*** | | | | diff --git a/tangle-a b/tangle-a
+*** | | | | new file mode 100644
+*** | | | | index 0000000..7898192
+*** | | | | --- /dev/null
+*** | | | | +++ b/tangle-a
+*** | | | | @@ -0,0 +1 @@
+*** | | | | +a
+*** | | | |
+*** * | | |   commit COMMIT_OBJECT_NAME
+*** |\ \ \ \  Merge: MERGE_PARENTS
+*** | | | | | Author: A U Thor <author@example.com>
+*** | | | | |
+*** | | | | |     Merge branch 'side'
+*** | | | | |
+*** | * | | | commit COMMIT_OBJECT_NAME
+*** | | |_|/  Author: A U Thor <author@example.com>
+*** | |/| |
+*** | | | |       side-2
+*** | | | |   ---
+*** | | | |    2 | 1 +
+*** | | | |    1 file changed, 1 insertion(+)
+*** | | | |
+*** | | | |   diff --git a/2 b/2
+*** | | | |   new file mode 100644
+*** | | | |   index 0000000..0cfbf08
+*** | | | |   --- /dev/null
+*** | | | |   +++ b/2
+*** | | | |   @@ -0,0 +1 @@
+*** | | | |   +2
+*** | | | |
+*** | * | | commit COMMIT_OBJECT_NAME
+*** | | | | Author: A U Thor <author@example.com>
+*** | | | |
+*** | | | |     side-1
+*** | | | | ---
+*** | | | |  1 | 1 +
+*** | | | |  1 file changed, 1 insertion(+)
+*** | | | |
+*** | | | | diff --git a/1 b/1
+*** | | | | new file mode 100644
+*** | | | | index 0000000..d00491f
+*** | | | | --- /dev/null
+*** | | | | +++ b/1
+*** | | | | @@ -0,0 +1 @@
+*** | | | | +1
+*** | | | |
+*** * | | | commit COMMIT_OBJECT_NAME
+*** | | | | Author: A U Thor <author@example.com>
+*** | | | |
+*** | | | |     Second
+*** | | | | ---
+*** | | | |  one | 1 +
+*** | | | |  1 file changed, 1 insertion(+)
+*** | | | |
+*** | | | | diff --git a/one b/one
+*** | | | | new file mode 100644
+*** | | | | index 0000000..9a33383
+*** | | | | --- /dev/null
+*** | | | | +++ b/one
+*** | | | | @@ -0,0 +1 @@
+*** | | | | +case
+*** | | | |
+*** * | | | commit COMMIT_OBJECT_NAME
+*** | |_|/  Author: A U Thor <author@example.com>
+*** |/| |
+*** | | |       sixth
+*** | | |   ---
+*** | | |    a/two | 1 -
+*** | | |    1 file changed, 1 deletion(-)
+*** | | |
+*** | | |   diff --git a/a/two b/a/two
+*** | | |   deleted file mode 100644
+*** | | |   index 9245af5..0000000
+*** | | |   --- a/a/two
+*** | | |   +++ /dev/null
+*** | | |   @@ -1 +0,0 @@
+*** | | |   -ni
+*** | | |
+*** * | | commit COMMIT_OBJECT_NAME
+*** | | | Author: A U Thor <author@example.com>
+*** | | |
+*** | | |     fifth
+*** | | | ---
+*** | | |  a/two | 1 +
+*** | | |  1 file changed, 1 insertion(+)
+*** | | |
+*** | | | diff --git a/a/two b/a/two
+*** | | | new file mode 100644
+*** | | | index 0000000..9245af5
+*** | | | --- /dev/null
+*** | | | +++ b/a/two
+*** | | | @@ -0,0 +1 @@
+*** | | | +ni
+*** | | |
+*** * | | commit COMMIT_OBJECT_NAME
+*** |/ /  Author: A U Thor <author@example.com>
+*** | |
+*** | |       fourth
+*** | |   ---
+*** | |    ein | 1 +
+*** | |    1 file changed, 1 insertion(+)
+*** | |
+*** | |   diff --git a/ein b/ein
+*** | |   new file mode 100644
+*** | |   index 0000000..9d7e69f
+*** | |   --- /dev/null
+*** | |   +++ b/ein
+*** | |   @@ -0,0 +1 @@
+*** | |   +ichi
+*** | |
+*** * | commit COMMIT_OBJECT_NAME
+*** |/  Author: A U Thor <author@example.com>
+*** |
+*** |       third
+*** |   ---
+*** |    ichi | 1 +
+*** |    one  | 1 -
+*** |    2 files changed, 1 insertion(+), 1 deletion(-)
+*** |
+*** |   diff --git a/ichi b/ichi
+*** |   new file mode 100644
+*** |   index 0000000..9d7e69f
+*** |   --- /dev/null
+*** |   +++ b/ichi
+*** |   @@ -0,0 +1 @@
+*** |   +ichi
+*** |   diff --git a/one b/one
+*** |   deleted file mode 100644
+*** |   index 9d7e69f..0000000
+*** |   --- a/one
+*** |   +++ /dev/null
+*** |   @@ -1 +0,0 @@
+*** |   -ichi
+*** |
+*** * commit COMMIT_OBJECT_NAME
+*** | Author: A U Thor <author@example.com>
+*** |
+*** |     second
+*** | ---
+*** |  one | 2 +-
+*** |  1 file changed, 1 insertion(+), 1 deletion(-)
+*** |
+*** | diff --git a/one b/one
+*** | index 5626abf..9d7e69f 100644
+*** | --- a/one
+*** | +++ b/one
+*** | @@ -1 +1 @@
+*** | -one
+*** | +ichi
+*** |
+*** * commit COMMIT_OBJECT_NAME
+***   Author: A U Thor <author@example.com>
+***
+***       initial
+***   ---
+***    one | 1 +
+***    1 file changed, 1 insertion(+)
+***
+***   diff --git a/one b/one
+***   new file mode 100644
+***   index 0000000..5626abf
+***   --- /dev/null
+***   +++ b/one
+***   @@ -0,0 +1 @@
+***   +one
+EOF
+
+test_expect_success 'log --line-prefix="*** " --graph with diff and stats' '
+	git log --line-prefix="*** " --no-renames --graph --pretty=short --stat -p >actual &&
+	sanitize_output >actual.sanitized <actual &&
+	test_i18ncmp expect actual.sanitized
+'
+
 test_expect_success 'dotdot is a parent directory' '
 	mkdir -p a/b &&
 	( echo sixth && echo fifth ) >expect &&