[PATCH v2] Make find_commit_subject() more robust

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

Just like the pretty printing machinery, we should simply ignore empty
lines at the beginning of the commit messages.

This discrepancy was noticed when an early version of the rebase--helper
produced commit objects with more than one empty line between the header
and the commit message.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
Published-As: https://github.com/dscho/git/releases/tag/leading-empty-lines-v2

	git blame seemed to be the most accessible user of
	find_commit_subject()...

 commit.c                 |  2 ++
 t/t8008-blame-formats.sh | 17 +++++++++++++++++
 2 files changed, 19 insertions(+)
Interdiff vs v1:

 diff --git a/t/t8008-blame-formats.sh b/t/t8008-blame-formats.sh
 index 29f84a6..03bd313 100755
 --- a/t/t8008-blame-formats.sh
 +++ b/t/t8008-blame-formats.sh
 @@ -87,4 +87,21 @@ test_expect_success 'blame --line-porcelain output' '
  	test_cmp expect actual
  '
  
 +test_expect_success '--porcelain detects first non-empty line as subject' '
 +	(
 +		GIT_INDEX_FILE=.git/tmp-index &&
 +		export GIT_INDEX_FILE &&
 +		echo "This is it" >single-file &&
 +		git add single-file &&
 +		tree=$(git write-tree) &&
 +		commit=$(printf "%s\n%s\n%s\n\n\noneline\n\nbody\n" \
 +			"tree $tree" \
 +			"author A <a@b.c> 123456789 +0000" \
 +			"committer C <c@d.e> 123456789 +0000" |
 +		git hash-object -w -t commit --stdin) &&
 +		git blame --porcelain $commit -- single-file >output &&
 +		grep "^summary oneline$" output
 +	)
 +'
 +
  test_done


diff --git a/commit.c b/commit.c
index 3f4f371..7b00989 100644
--- a/commit.c
+++ b/commit.c
@@ -415,6 +415,8 @@ int find_commit_subject(const char *commit_buffer, const char **subject)
 		p++;
 	if (*p) {
 		p += 2;
+		while (*p == '\n')
+			p++;
 		for (eol = p; *eol && *eol != '\n'; eol++)
 			; /* do nothing */
 	} else
diff --git a/t/t8008-blame-formats.sh b/t/t8008-blame-formats.sh
index 29f84a6..03bd313 100755
--- a/t/t8008-blame-formats.sh
+++ b/t/t8008-blame-formats.sh
@@ -87,4 +87,21 @@ test_expect_success 'blame --line-porcelain output' '
 	test_cmp expect actual
 '
 
+test_expect_success '--porcelain detects first non-empty line as subject' '
+	(
+		GIT_INDEX_FILE=.git/tmp-index &&
+		export GIT_INDEX_FILE &&
+		echo "This is it" >single-file &&
+		git add single-file &&
+		tree=$(git write-tree) &&
+		commit=$(printf "%s\n%s\n%s\n\n\noneline\n\nbody\n" \
+			"tree $tree" \
+			"author A <a@b.c> 123456789 +0000" \
+			"committer C <c@d.e> 123456789 +0000" |
+		git hash-object -w -t commit --stdin) &&
+		git blame --porcelain $commit -- single-file >output &&
+		grep "^summary oneline$" output
+	)
+'
+
 test_done
-- 
2.9.0.118.g0e1a633

base-commit: ab7797dbe95fff38d9265869ea367020046db118