docs: warn about possible '=' in clean/smudge filter process values

A pathname value in a clean/smudge filter process "key=value" pair can
contain the '=' character (introduced in edcc858). Make the user aware
of this issue in the docs, add a corresponding test case, and fix the
issue in filter process value parser of the example implementation in
contrib.

Signed-off-by: Lars Schneider <larsxschneider@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/gitattributes.txt

@@ -435,7 +435,9 @@ to filter relative to the repository root. Right after the flush packet
 Git sends the content split in zero or more pkt-line packets and a
 flush packet to terminate content. Please note, that the filter
 must not send any response before it received the content and the
-final flush packet.
+final flush packet. Also note that the "value" of a "key=value" pair
+can contain the "=" character whereas the key would never contain
+that character.
 ------------------------
 packet:          git> command=smudge
 packet:          git> pathname=path/testfile.dat

contrib/long-running-filter/example.pl

@@ -81,8 +81,12 @@ packet_txt_write("capability=smudge");
 packet_flush();
 
 while (1) {
-	my ($command)  = packet_txt_read() =~ /^command=([^=]+)$/;
-	my ($pathname) = packet_txt_read() =~ /^pathname=([^=]+)$/;
+	my ($command)  = packet_txt_read() =~ /^command=(.+)$/;
+	my ($pathname) = packet_txt_read() =~ /^pathname=(.+)$/;
+
+	if ( $pathname eq "" ) {
+		die "bad pathname '$pathname'";
+	}
 
 	packet_bin_read();
 

t/t0021-conversion.sh

@@ -91,7 +91,7 @@ test_expect_success setup '
 	git checkout -- test test.t test.i &&
 
 	echo "content-test2" >test2.o &&
-	echo "content-test3 - filename with special characters" >"test3 '\''sq'\'',\$x.o"
+	echo "content-test3 - filename with special characters" >"test3 '\''sq'\'',\$x=.o"
 '
 
 script='s/^\$Id: \([0-9a-f]*\) \$/\1/p'
@@ -357,12 +357,12 @@ test_expect_success PERL 'required process filter should filter data' '
 		cp "$TEST_ROOT/test.o" test.r &&
 		cp "$TEST_ROOT/test2.o" test2.r &&
 		mkdir testsubdir &&
-		cp "$TEST_ROOT/test3 '\''sq'\'',\$x.o" "testsubdir/test3 '\''sq'\'',\$x.r" &&
+		cp "$TEST_ROOT/test3 '\''sq'\'',\$x=.o" "testsubdir/test3 '\''sq'\'',\$x=.r" &&
 		>test4-empty.r &&
 
 		S=$(file_size test.r) &&
 		S2=$(file_size test2.r) &&
-		S3=$(file_size "testsubdir/test3 '\''sq'\'',\$x.r") &&
+		S3=$(file_size "testsubdir/test3 '\''sq'\'',\$x=.r") &&
 
 		filter_git add . &&
 		cat >expected.log <<-EOF &&
@@ -371,7 +371,7 @@ test_expect_success PERL 'required process filter should filter data' '
 			IN: clean test.r $S [OK] -- OUT: $S . [OK]
 			IN: clean test2.r $S2 [OK] -- OUT: $S2 . [OK]
 			IN: clean test4-empty.r 0 [OK] -- OUT: 0  [OK]
-			IN: clean testsubdir/test3 '\''sq'\'',\$x.r $S3 [OK] -- OUT: $S3 . [OK]
+			IN: clean testsubdir/test3 '\''sq'\'',\$x=.r $S3 [OK] -- OUT: $S3 . [OK]
 			STOP
 		EOF
 		test_cmp_count expected.log rot13-filter.log &&
@@ -383,23 +383,23 @@ test_expect_success PERL 'required process filter should filter data' '
 			IN: clean test.r $S [OK] -- OUT: $S . [OK]
 			IN: clean test2.r $S2 [OK] -- OUT: $S2 . [OK]
 			IN: clean test4-empty.r 0 [OK] -- OUT: 0  [OK]
-			IN: clean testsubdir/test3 '\''sq'\'',\$x.r $S3 [OK] -- OUT: $S3 . [OK]
+			IN: clean testsubdir/test3 '\''sq'\'',\$x=.r $S3 [OK] -- OUT: $S3 . [OK]
 			IN: clean test.r $S [OK] -- OUT: $S . [OK]
 			IN: clean test2.r $S2 [OK] -- OUT: $S2 . [OK]
 			IN: clean test4-empty.r 0 [OK] -- OUT: 0  [OK]
-			IN: clean testsubdir/test3 '\''sq'\'',\$x.r $S3 [OK] -- OUT: $S3 . [OK]
+			IN: clean testsubdir/test3 '\''sq'\'',\$x=.r $S3 [OK] -- OUT: $S3 . [OK]
 			STOP
 		EOF
 		test_cmp_count expected.log rot13-filter.log &&
 
-		rm -f test2.r "testsubdir/test3 '\''sq'\'',\$x.r" &&
+		rm -f test2.r "testsubdir/test3 '\''sq'\'',\$x=.r" &&
 
 		filter_git checkout --quiet --no-progress . &&
 		cat >expected.log <<-EOF &&
 			START
 			init handshake complete
 			IN: smudge test2.r $S2 [OK] -- OUT: $S2 . [OK]
-			IN: smudge testsubdir/test3 '\''sq'\'',\$x.r $S3 [OK] -- OUT: $S3 . [OK]
+			IN: smudge testsubdir/test3 '\''sq'\'',\$x=.r $S3 [OK] -- OUT: $S3 . [OK]
 			STOP
 		EOF
 		test_cmp_exclude_clean expected.log rot13-filter.log &&
@@ -420,14 +420,14 @@ test_expect_success PERL 'required process filter should filter data' '
 			IN: smudge test.r $S [OK] -- OUT: $S . [OK]
 			IN: smudge test2.r $S2 [OK] -- OUT: $S2 . [OK]
 			IN: smudge test4-empty.r 0 [OK] -- OUT: 0  [OK]
-			IN: smudge testsubdir/test3 '\''sq'\'',\$x.r $S3 [OK] -- OUT: $S3 . [OK]
+			IN: smudge testsubdir/test3 '\''sq'\'',\$x=.r $S3 [OK] -- OUT: $S3 . [OK]
 			STOP
 		EOF
 		test_cmp_exclude_clean expected.log rot13-filter.log &&
 
 		test_cmp_committed_rot13 "$TEST_ROOT/test.o" test.r &&
 		test_cmp_committed_rot13 "$TEST_ROOT/test2.o" test2.r &&
-		test_cmp_committed_rot13 "$TEST_ROOT/test3 '\''sq'\'',\$x.o" "testsubdir/test3 '\''sq'\'',\$x.r"
+		test_cmp_committed_rot13 "$TEST_ROOT/test3 '\''sq'\'',\$x=.o" "testsubdir/test3 '\''sq'\'',\$x=.r"
 	)
 '
 

t/t0021/rot13-filter.pl

@@ -109,14 +109,18 @@ print $debug "init handshake complete\n";
 $debug->flush();
 
 while (1) {
-	my ($command) = packet_txt_read() =~ /^command=([^=]+)$/;
+	my ($command) = packet_txt_read() =~ /^command=(.+)$/;
 	print $debug "IN: $command";
 	$debug->flush();
 
-	my ($pathname) = packet_txt_read() =~ /^pathname=([^=]+)$/;
+	my ($pathname) = packet_txt_read() =~ /^pathname=(.+)$/;
 	print $debug " $pathname";
 	$debug->flush();
 
+	if ( $pathname eq "" ) {
+		die "bad pathname '$pathname'";
+	}
+
 	# Flush
 	packet_bin_read();