[PATCH] squash! diff: add --diff-line-prefix option for passing in a prefix

[Johannes Schindelin <johannes.schindelin@gmx.de>]

The '>' character is not a legal part of filenames on Windows. So let's
just not use it in Git's source code. This poses a challenge in the test
script t4013 which distills command-lines into file names (so that the
expected outcome can be stored in files with said names).

We have to take particular care not to confound the existing conversion
of unwanted characters to underscores with the new substitution of '>':
the existing conversion chose to collapse runs of multiple unwanted
characters into a single underscore. If we allowed '>' to be collapsed,
too, the file name generated from the command "diff [...]=-- [...]"
would be identical to the one generated from "diff [...]=--> [...]".

Please squash this patch into
3c90ffd2f01e2d0d080c8e42df2ee89709b324de

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
Published-As: https://github.com/dscho/git/releases/tag/mingw-t4013-v1
Fetch-It-Via: git fetch https://github.com/dscho/git mingw-t4013-v1

	For the record: this prevented my beautiful CI jobs from even
	checking out the source code for `pu` in the last days.

	Junio, please let me know if you would prefer this as a separate
	patch.

 t/t4013-diff-various.sh                                                 | 2 +-
 ...aster^_side => diff.diff_--diff-line-prefix=--__master_master^_side} | 0
 2 files changed, 1 insertion(+), 1 deletion(-)
 rename t/t4013/{diff.diff_--diff-line-prefix=-->_master_master^_side => diff.diff_--diff-line-prefix=--__master_master^_side} (100%)

diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
index 5204645..84e2ee0 100755
--- a/t/t4013-diff-various.sh
+++ b/t/t4013-diff-various.sh
@@ -115,7 +115,7 @@ do
 	case "$cmd" in
 	'' | '#'*) continue ;;
 	esac
-	test=$(echo "$cmd" | sed -e 's|[/ ][/ ]*|_|g')
+	test=$(echo "$cmd" | sed -e 's|[/ ][/ ]*|_|g' -e 'y/>/_/')
 	pfx=$(printf "%04d" $test_count)
 	expect="$TEST_DIRECTORY/t4013/diff.$test"
 	actual="$pfx-diff.$test"
diff --git a/t/t4013/diff.diff_--diff-line-prefix=-->_master_master^_side b/t/t4013/diff.diff_--diff-line-prefix=--__master_master^_side
similarity index 100%
rename from t/t4013/diff.diff_--diff-line-prefix=-->_master_master^_side
rename to t/t4013/diff.diff_--diff-line-prefix=--__master_master^_side
-- 
2.9.2.691.g78954f3

base-commit: 945e149951a152207b56d5e49ff5167d151a4c89