Merge branch 'jk/blame-fixes' into maint

"git blame --porcelain" misidentified the "previous" <commit, path>
pair (aka "source") when contents came from two or more files.

* jk/blame-fixes:
  blame: output porcelain "previous" header for each file
  blame: handle --no-abbrev
  blame: fix alignment with --abbrev=40

3 files changed, 166 insertions, 10 deletions

diff --git a/builtin/blame.c b/builtin/blame.c
index 4ddfadb71..3aae19a0f 100644
--- a/builtin/blame.c
+++ b/builtin/blame.c
@@ -1700,13 +1700,23 @@ static void get_commit_info(struct commit *commit,
 }
 
 /*
+ * Write out any suspect information which depends on the path. This must be
+ * handled separately from emit_one_suspect_detail(), because a given commit
+ * may have changes in multiple paths. So this needs to appear each time
+ * we mention a new group.
+ *
  * To allow LF and other nonportable characters in pathnames,
  * they are c-style quoted as needed.
  */
-static void write_filename_info(const char *path)
+static void write_filename_info(struct origin *suspect)
 {
+	if (suspect->previous) {
+		struct origin *prev = suspect->previous;
+		printf("previous %s ", oid_to_hex(&prev->commit->object.oid));
+		write_name_quoted(prev->path, stdout, '\n');
+	}
 	printf("filename ");
-	write_name_quoted(path, stdout, '\n');
+	write_name_quoted(suspect->path, stdout, '\n');
 }
 
 /*
@@ -1735,11 +1745,6 @@ static int emit_one_suspect_detail(struct origin *suspect, int repeat)
 	printf("summary %s\n", ci.summary.buf);
 	if (suspect->commit->object.flags & UNINTERESTING)
 		printf("boundary\n");
-	if (suspect->previous) {
-		struct origin *prev = suspect->previous;
-		printf("previous %s ", oid_to_hex(&prev->commit->object.oid));
-		write_name_quoted(prev->path, stdout, '\n');
-	}
 
 	commit_info_destroy(&ci);
 
@@ -1760,7 +1765,7 @@ static void found_guilty_entry(struct blame_entry *ent,
 		       oid_to_hex(&suspect->commit->object.oid),
 		       ent->s_lno + 1, ent->lno + 1, ent->num_lines);
 		emit_one_suspect_detail(suspect, 0);
-		write_filename_info(suspect->path);
+		write_filename_info(suspect);
 		maybe_flush_or_die(stdout, "stdout");
 	}
 	pi->blamed_lines += ent->num_lines;
@@ -1884,7 +1889,7 @@ static void emit_porcelain_details(struct origin *suspect, int repeat)
 {
 	if (emit_one_suspect_detail(suspect, repeat) ||
 	    (suspect->commit->object.flags & MORE_THAN_ONE_PATH))
-		write_filename_info(suspect->path);
+		write_filename_info(suspect);
 }
 
 static void emit_porcelain(struct scoreboard *sb, struct blame_entry *ent,
@@ -2656,9 +2661,11 @@ parse_done:
 	} else if (show_progress < 0)
 		show_progress = isatty(2);
 
-	if (0 < abbrev)
+	if (0 < abbrev && abbrev < GIT_SHA1_HEXSZ)
 		/* one more abbrev length is needed for the boundary commit */
 		abbrev++;
+	else if (!abbrev)
+		abbrev = GIT_SHA1_HEXSZ;
 
 	if (revs_file && read_ancestry(revs_file))
 		die_errno("reading graft file '%s' failed", revs_file);
diff --git a/t/t8002-blame.sh b/t/t8002-blame.sh
index ab79de954..380e1c105 100755
--- a/t/t8002-blame.sh
+++ b/t/t8002-blame.sh
@@ -86,4 +86,36 @@ test_expect_success 'blame with showEmail config true' '
 	test_cmp expected_n result
 '
 
+test_expect_success 'set up abbrev tests' '
+	test_commit abbrev &&
+	sha1=$(git rev-parse --verify HEAD) &&
+	check_abbrev () {
+		expect=$1; shift
+		echo $sha1 | cut -c 1-$expect >expect &&
+		git blame "$@" abbrev.t >actual &&
+		perl -lne "/[0-9a-f]+/ and print \$&" <actual >actual.sha &&
+		test_cmp expect actual.sha
+	}
+'
+
+test_expect_success 'blame --abbrev=<n> works' '
+	# non-boundary commits get +1 for alignment
+	check_abbrev 31 --abbrev=30 HEAD &&
+	check_abbrev 30 --abbrev=30 ^HEAD
+'
+
+test_expect_success 'blame -l aligns regular and boundary commits' '
+	check_abbrev 40 -l HEAD &&
+	check_abbrev 39 -l ^HEAD
+'
+
+test_expect_success 'blame --abbrev=40 behaves like -l' '
+	check_abbrev 40 --abbrev=40 HEAD &&
+	check_abbrev 39 --abbrev=40 ^HEAD
+'
+
+test_expect_success '--no-abbrev works like --abbrev=40' '
+	check_abbrev 40 --no-abbrev
+'
+
 test_done
diff --git a/t/t8011-blame-split-file.sh b/t/t8011-blame-split-file.sh
new file mode 100755
index 000000000..831125047
--- /dev/null
+++ b/t/t8011-blame-split-file.sh
@@ -0,0 +1,117 @@
+#!/bin/sh
+
+test_description='
+The general idea is that we have a single file whose lines come from
+multiple other files, and those individual files were modified in the same
+commits. That means that we will see the same commit in multiple contexts,
+and each one should be attributed to the correct file.
+
+Note that we need to use "blame -C" to find the commit for all lines. We will
+not bother testing that the non-C case fails to find it. That is how blame
+behaves now, but it is not a property we want to make sure is retained.
+'
+. ./test-lib.sh
+
+# help avoid typing and reading long strings of similar lines
+# in the tests below
+generate_expect () {
+	while read nr data
+	do
+		i=0
+		while test $i -lt $nr
+		do
+			echo $data
+			i=$((i + 1))
+		done
+	done
+}
+
+test_expect_success 'setup split file case' '
+	# use lines long enough to trigger content detection
+	test_seq 1000 1010 >one &&
+	test_seq 2000 2010 >two &&
+	git add one two &&
+	test_commit base &&
+
+	sed "6s/^/modified /" <one >one.tmp &&
+	mv one.tmp one &&
+	sed "6s/^/modified /" <two >two.tmp &&
+	mv two.tmp two &&
+	git add -u &&
+	test_commit modified &&
+
+	cat one two >combined &&
+	git add combined &&
+	git rm one two &&
+	test_commit combined
+'
+
+test_expect_success 'setup simulated porcelain' '
+	# This just reads porcelain-ish output and tries
+	# to output the value of a given field for each line (either by
+	# reading the field that accompanies this line, or referencing
+	# the information found last time the commit was mentioned).
+	cat >read-porcelain.pl <<-\EOF
+	my $field = shift;
+	while (<>) {
+		if (/^[0-9a-f]{40} /) {
+			flush();
+			$hash = $&;
+		} elsif (/^$field (.*)/) {
+			$cache{$hash} = $1;
+		}
+	}
+	flush();
+
+	sub flush {
+		return unless defined $hash;
+		if (defined $cache{$hash}) {
+			print "$cache{$hash}\n";
+		} else {
+			print "NONE\n";
+		}
+	}
+	EOF
+'
+
+for output in porcelain line-porcelain
+do
+	test_expect_success "generate --$output output" '
+		git blame --root -C --$output combined >output
+	'
+
+	test_expect_success "$output output finds correct commits" '
+		generate_expect >expect <<-\EOF &&
+		5 base
+		1 modified
+		10 base
+		1 modified
+		5 base
+		EOF
+		perl read-porcelain.pl summary <output >actual &&
+		test_cmp expect actual
+	'
+
+	test_expect_success "$output output shows correct filenames" '
+		generate_expect >expect <<-\EOF &&
+		11 one
+		11 two
+		EOF
+		perl read-porcelain.pl filename <output >actual &&
+		test_cmp expect actual
+	'
+
+	test_expect_success "$output output shows correct previous pointer" '
+		generate_expect >expect <<-EOF &&
+		5 NONE
+		1 $(git rev-parse modified^) one
+		10 NONE
+		1 $(git rev-parse modified^) two
+		5 NONE
+		EOF
+		perl read-porcelain.pl previous <output >actual &&
+		test_cmp expect actual
+	'
+done
+
+test_done