graph: fix coloring of octopus dashes

In 04005834ed ("log: fix coloring of certain octopus merge shapes",
2018-09-01) there is a fix for the coloring of dashes following an
octopus merge. It makes a distinction between the case where all parents
introduce a new column, versus the case where the first parent collapses
into an existing column:

        | *-.           | *-.
        | |\ \          | |\ \
        | | | |         |/ / /

The latter case means that the columns for the merge parents begin one
place to the left in the `new_columns` array compared to the former
case.

However, the implementation only works if the commit's parents are kept
in order as they map onto the visual columns, as we get the colors by
iterating over `new_columns` as we print the dashes. In general, the
commit's parents can arbitrarily merge with existing columns, and change
their ordering in the process.

For example, in the following diagram, the number of each column
indicates which commit parent appears in each column.

        | | *---.
        | | |\ \ \
        | | |/ / /
        | |/| | /
        | |_|_|/
        |/| | |
        3 1 0 2

If the columns are colored (red, green, yellow, blue), then the dashes
will currently be colored yellow and blue, whereas they should be blue
and red.

To fix this, we need to look up each column in the `mapping` array,
which before the `GRAPH_COLLAPSING` state indicates which logical column
is displayed in each visual column. This implementation is simpler as it
doesn't have any edge cases, and it also handles how left-skewed first
parents are now displayed:

        | *-.
        |/|\ \
        | | | |
        0 1 2 3

The color of the first dashes is always the color found in `mapping` two
columns to the right of the commit symbol. Because commits are displayed
after all edges have been collapsed together and the visual columns
match the logical ones, we can find the visual offset of the commit
symbol using `commit_index`.

Signed-off-by: James Coglan <jcoglan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 5 insertions, 5 deletions

diff --git a/t/t4214-log-graph-octopus.sh b/t/t4214-log-graph-octopus.sh
index 21bc600a82..40d27db674 100755
--- a/t/t4214-log-graph-octopus.sh
+++ b/t/t4214-log-graph-octopus.sh
@@ -121,7 +121,7 @@ test_expect_success 'log --graph with normal octopus merge and child, no color'
 	test_cmp expect.uncolored actual
 '
 
-test_expect_failure 'log --graph with normal octopus and child merge with colors' '
+test_expect_success 'log --graph with normal octopus and child merge with colors' '
 	cat >expect.colors <<-\EOF &&
 	* after-merge
 	*<BLUE>-<RESET><BLUE>-<RESET><MAGENTA>-<RESET><MAGENTA>.<RESET>   octopus-merge
@@ -161,7 +161,7 @@ test_expect_success 'log --graph with tricky octopus merge and its child, no col
 	test_cmp expect.uncolored actual
 '
 
-test_expect_failure 'log --graph with tricky octopus merge and its child with colors' '
+test_expect_success 'log --graph with tricky octopus merge and its child with colors' '
 	test_config log.graphColors red,green,yellow,blue,magenta,cyan &&
 	cat >expect.colors <<-\EOF &&
 	* left
@@ -205,7 +205,7 @@ test_expect_success 'log --graph with crossover in octopus merge, no color' '
 	test_cmp expect.uncolored actual
 '
 
-test_expect_failure 'log --graph with crossover in octopus merge with colors' '
+test_expect_success 'log --graph with crossover in octopus merge with colors' '
 	test_config log.graphColors red,green,yellow,blue,magenta,cyan &&
 	cat >expect.colors <<-\EOF &&
 	* after-4
@@ -253,7 +253,7 @@ test_expect_success 'log --graph with crossover in octopus merge and its child,
 	test_cmp expect.uncolored actual
 '
 
-test_expect_failure 'log --graph with crossover in octopus merge and its child with colors' '
+test_expect_success 'log --graph with crossover in octopus merge and its child with colors' '
 	test_config log.graphColors red,green,yellow,blue,magenta,cyan &&
 	cat >expect.colors <<-\EOF &&
 	* after-4
@@ -349,7 +349,7 @@ test_expect_success 'log --graph with unrelated commit and octopus child, no col
 	test_cmp expect.uncolored actual
 '
 
-test_expect_failure 'log --graph with unrelated commit and octopus child with colors' '
+test_expect_success 'log --graph with unrelated commit and octopus child with colors' '
 	test_config log.graphColors red,green,yellow,blue,magenta,cyan &&
 	cat >expect.colors <<-\EOF &&
 	* after-initial