vcs-svn: set up channel to read fast-import cat-blob response

Set up some plumbing: teach the svndump lib to pass a file descriptor
number to the fast_export lib, representing where cat-blob/ls
responses can be read from, and add a get_response_line helper
function to the fast_export lib to read a line from that file.

Unfortunately this means that svn-fe needs file descriptor 3 to be
redirected from somewhere (preferrably the cat-blob stream of a
fast-import backend); otherwise it will fail:

	$ svndump <path> | svn-fe
	fatal: cannot read from file descriptor 3: Bad file descriptor

For the moment, "svn-fe 3</dev/null" works as a workaround but it
will not work for very long.  A fast-import backend that can retrieve
old commits is needed in order to be able to fulfill svn
"Node-copyfrom-rev" requests that refer to revs from a previous run.

[jn: with new change description]

Based-on-patch-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: David Barr <david.barr@cordelta.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>

contrib/svn-fe/svn-fe.txt

@@ -7,7 +7,11 @@ svn-fe - convert an SVN "dumpfile" to a fast-import stream
 
 SYNOPSIS
 --------
-svnadmin dump --incremental REPO | svn-fe [url] | git fast-import
+[verse]
+mkfifo backchannel &&
+svnadmin dump --incremental REPO |
+	svn-fe [url] 3<backchannel |
+	git fast-import --cat-blob-fd=3 3>backchannel
 
 DESCRIPTION
 -----------

t/t9010-svn-fe.sh

@@ -5,8 +5,26 @@ test_description='check svn dumpfile importer'
 . ./test-lib.sh
 
 reinit_git () {
+	if ! test_declared_prereq PIPE
+	then
+		echo >&4 "reinit_git: need to declare PIPE prerequisite"
+		return 127
+	fi
 	rm -fr .git &&
-	git init
+	rm -f stream backflow &&
+	git init &&
+	mkfifo stream backflow
+}
+
+try_dump () {
+	input=$1 &&
+	maybe_fail=${2:+test_$2} &&
+
+	{
+		$maybe_fail test-svn-fe "$input" >stream 3<backflow &
+	} &&
+	git fast-import --cat-blob-fd=3 <stream 3>backflow &&
+	wait $!
 }
 
 properties () {
@@ -35,21 +53,27 @@ text_no_props () {
 
 >empty
 
-test_expect_success 'empty dump' '
+test_expect_success 'setup: have pipes?' '
+	rm -f frob &&
+	if mkfifo frob
+	then
+		test_set_prereq PIPE
+	fi
+'
+
+test_expect_success PIPE 'empty dump' '
 	reinit_git &&
 	echo "SVN-fs-dump-format-version: 2" >input &&
-	test-svn-fe input >stream &&
-	git fast-import <stream
+	try_dump input
 '
 
-test_expect_success 'v4 dumps not supported' '
+test_expect_success PIPE 'v4 dumps not supported' '
 	reinit_git &&
 	echo "SVN-fs-dump-format-version: 4" >v4.dump &&
-	test_must_fail test-svn-fe v4.dump >stream &&
-	test_cmp empty stream
+	try_dump v4.dump must_fail
 '
 
-test_expect_failure 'empty revision' '
+test_expect_failure PIPE 'empty revision' '
 	reinit_git &&
 	printf "rev <nobody, nobody@local>: %s\n" "" "" >expect &&
 	cat >emptyrev.dump <<-\EOF &&
@@ -64,13 +88,12 @@ test_expect_failure 'empty revision' '
 	Content-length: 0
 
 	EOF
-	test-svn-fe emptyrev.dump >stream &&
-	git fast-import <stream &&
+	try_dump emptyrev.dump &&
 	git log -p --format="rev <%an, %ae>: %s" HEAD >actual &&
 	test_cmp expect actual
 '
 
-test_expect_success 'empty properties' '
+test_expect_success PIPE 'empty properties' '
 	reinit_git &&
 	printf "rev <nobody, nobody@local>: %s\n" "" "" >expect &&
 	cat >emptyprop.dump <<-\EOF &&
@@ -88,13 +111,12 @@ test_expect_success 'empty properties' '
 
 	PROPS-END
 	EOF
-	test-svn-fe emptyprop.dump >stream &&
-	git fast-import <stream &&
+	try_dump emptyprop.dump &&
 	git log -p --format="rev <%an, %ae>: %s" HEAD >actual &&
 	test_cmp expect actual
 '
 
-test_expect_success 'author name and commit message' '
+test_expect_success PIPE 'author name and commit message' '
 	reinit_git &&
 	echo "<author@example.com, author@example.com@local>" >expect.author &&
 	cat >message <<-\EOF &&
@@ -121,15 +143,14 @@ test_expect_success 'author name and commit message' '
 		echo &&
 		cat props
 	} >log.dump &&
-	test-svn-fe log.dump >stream &&
-	git fast-import <stream &&
+	try_dump log.dump &&
 	git log -p --format="%B" HEAD >actual.log &&
 	git log --format="<%an, %ae>" >actual.author &&
 	test_cmp message actual.log &&
 	test_cmp expect.author actual.author
 '
 
-test_expect_success 'unsupported properties are ignored' '
+test_expect_success PIPE 'unsupported properties are ignored' '
 	reinit_git &&
 	echo author >expect &&
 	cat >extraprop.dump <<-\EOF &&
@@ -149,13 +170,12 @@ test_expect_success 'unsupported properties are ignored' '
 	author
 	PROPS-END
 	EOF
-	test-svn-fe extraprop.dump >stream &&
-	git fast-import <stream &&
+	try_dump extraprop.dump &&
 	git log -p --format=%an HEAD >actual &&
 	test_cmp expect actual
 '
 
-test_expect_failure 'timestamp and empty file' '
+test_expect_failure PIPE 'timestamp and empty file' '
 	echo author@example.com >expect.author &&
 	echo 1999-01-01 >expect.date &&
 	echo file >expect.files &&
@@ -186,8 +206,7 @@ test_expect_failure 'timestamp and empty file' '
 
 		EOF
 	} >emptyfile.dump &&
-	test-svn-fe emptyfile.dump >stream &&
-	git fast-import <stream &&
+	try_dump emptyfile.dump &&
 	git log --format=%an HEAD >actual.author &&
 	git log --date=short --format=%ad HEAD >actual.date &&
 	git ls-tree -r --name-only HEAD >actual.files &&
@@ -198,7 +217,7 @@ test_expect_failure 'timestamp and empty file' '
 	test_cmp empty file
 '
 
-test_expect_success 'directory with files' '
+test_expect_success PIPE 'directory with files' '
 	reinit_git &&
 	printf "%s\n" directory/file1 directory/file2 >expect.files &&
 	echo hi >hi &&
@@ -242,8 +261,7 @@ test_expect_success 'directory with files' '
 		EOF
 		text_no_props hi
 	} >directory.dump &&
-	test-svn-fe directory.dump >stream &&
-	git fast-import <stream &&
+	try_dump directory.dump &&
 
 	git ls-tree -r --name-only HEAD >actual.files &&
 	git checkout HEAD directory &&
@@ -252,7 +270,8 @@ test_expect_success 'directory with files' '
 	test_cmp hi directory/file2
 '
 
-test_expect_success 'node without action' '
+test_expect_success PIPE 'node without action' '
+	reinit_git &&
 	cat >inaction.dump <<-\EOF &&
 	SVN-fs-dump-format-version: 3
 
@@ -269,10 +288,11 @@ test_expect_success 'node without action' '
 
 	PROPS-END
 	EOF
-	test_must_fail test-svn-fe inaction.dump
+	try_dump inaction.dump must_fail
 '
 
-test_expect_success 'action: add node without text' '
+test_expect_success PIPE 'action: add node without text' '
+	reinit_git &&
 	cat >textless.dump <<-\EOF &&
 	SVN-fs-dump-format-version: 3
 
@@ -290,10 +310,10 @@ test_expect_success 'action: add node without text' '
 
 	PROPS-END
 	EOF
-	test_must_fail test-svn-fe textless.dump
+	try_dump textless.dump must_fail
 '
 
-test_expect_failure 'change file mode but keep old content' '
+test_expect_failure PIPE 'change file mode but keep old content' '
 	reinit_git &&
 	cat >expect <<-\EOF &&
 	OBJID
@@ -356,8 +376,7 @@ test_expect_failure 'change file mode but keep old content' '
 
 	PROPS-END
 	EOF
-	test-svn-fe filemode.dump >stream &&
-	git fast-import <stream &&
+	try_dump filemode.dump &&
 	{
 		git rev-list HEAD |
 		git diff-tree --root --stdin |
@@ -370,7 +389,7 @@ test_expect_failure 'change file mode but keep old content' '
 	test_cmp hello actual.target
 '
 
-test_expect_success 'change file mode and reiterate content' '
+test_expect_success PIPE 'change file mode and reiterate content' '
 	reinit_git &&
 	cat >expect <<-\EOF &&
 	OBJID
@@ -382,7 +401,7 @@ test_expect_success 'change file mode and reiterate content' '
 	EOF
 	echo "link hello" >expect.blob &&
 	echo hello >hello &&
-	cat >filemode.dump <<-\EOF &&
+	cat >filemode2.dump <<-\EOF &&
 	SVN-fs-dump-format-version: 3
 
 	Revision-number: 1
@@ -437,8 +456,7 @@ test_expect_success 'change file mode and reiterate content' '
 	PROPS-END
 	link hello
 	EOF
-	test-svn-fe filemode.dump >stream &&
-	git fast-import <stream &&
+	try_dump filemode2.dump &&
 	{
 		git rev-list HEAD |
 		git diff-tree --root --stdin |
@@ -451,7 +469,8 @@ test_expect_success 'change file mode and reiterate content' '
 	test_cmp hello actual.target
 '
 
-test_expect_success 'deltas not supported' '
+test_expect_success PIPE 'deltas not supported' '
+	reinit_git &&
 	{
 		# (old) h + (inline) ello + (old) \n
 		printf "SVNQ%b%b%s" "Q\003\006\005\004" "\001Q\0204\001\002" "ello" |
@@ -511,10 +530,10 @@ test_expect_success 'deltas not supported' '
 		echo PROPS-END &&
 		cat delta
 	} >delta.dump &&
-	test_must_fail test-svn-fe delta.dump
+	test_must_fail try_dump delta.dump
 '
 
-test_expect_success 'property deltas supported' '
+test_expect_success PIPE 'property deltas supported' '
 	reinit_git &&
 	cat >expect <<-\EOF &&
 	OBJID
@@ -570,8 +589,7 @@ test_expect_success 'property deltas supported' '
 		PROPS-END
 		EOF
 	} >propdelta.dump &&
-	test-svn-fe propdelta.dump >stream &&
-	git fast-import <stream &&
+	try_dump propdelta.dump &&
 	{
 		git rev-list HEAD |
 		git diff-tree --stdin |
@@ -580,7 +598,7 @@ test_expect_success 'property deltas supported' '
 	test_cmp expect actual
 '
 
-test_expect_success 'properties on /' '
+test_expect_success PIPE 'properties on /' '
 	reinit_git &&
 	cat <<-\EOF >expect &&
 	OBJID
@@ -625,8 +643,7 @@ test_expect_success 'properties on /' '
 
 	PROPS-END
 	EOF
-	test-svn-fe changeroot.dump >stream &&
-	git fast-import <stream &&
+	try_dump changeroot.dump &&
 	{
 		git rev-list HEAD |
 		git diff-tree --root --always --stdin |
@@ -635,7 +652,7 @@ test_expect_success 'properties on /' '
 	test_cmp expect actual
 '
 
-test_expect_success 'deltas for typechange' '
+test_expect_success PIPE 'deltas for typechange' '
 	reinit_git &&
 	cat >expect <<-\EOF &&
 	OBJID
@@ -711,8 +728,7 @@ test_expect_success 'deltas for typechange' '
 	PROPS-END
 	link testing 321
 	EOF
-	test-svn-fe deleteprop.dump >stream &&
-	git fast-import <stream &&
+	try_dump deleteprop.dump &&
 	{
 		git rev-list HEAD |
 		git diff-tree --root --stdin |
@@ -736,12 +752,12 @@ test_expect_success 'set up svn repo' '
 	fi
 '
 
-test_expect_success SVNREPO 't9135/svn.dump' '
-	git init simple-git &&
-	test-svn-fe "$TEST_DIRECTORY/t9135/svn.dump" >simple.fe &&
+test_expect_success SVNREPO,PIPE 't9135/svn.dump' '
+	mkdir -p simple-git &&
 	(
 		cd simple-git &&
-		git fast-import <../simple.fe
+		reinit_git &&
+		try_dump "$TEST_DIRECTORY/t9135/svn.dump"
 	) &&
 	(
 		cd simple-svnco &&

vcs-svn/fast_export.c

@@ -12,6 +12,24 @@
 #define MAX_GITSVN_LINE_LEN 4096
 
 static uint32_t first_commit_done;
+static struct line_buffer report_buffer = LINE_BUFFER_INIT;
+
+void fast_export_init(int fd)
+{
+	if (buffer_fdinit(&report_buffer, fd))
+		die_errno("cannot read from file descriptor %d", fd);
+}
+
+void fast_export_deinit(void)
+{
+	if (buffer_deinit(&report_buffer))
+		die_errno("error closing fast-import feedback stream");
+}
+
+void fast_export_reset(void)
+{
+	buffer_reset(&report_buffer);
+}
 
 void fast_export_delete(uint32_t depth, uint32_t *path)
 {
@@ -63,6 +81,16 @@ void fast_export_commit(uint32_t revision, uint32_t author, char *log,
 	printf("progress Imported commit %"PRIu32".\n\n", revision);
 }
 
+static const char *get_response_line(void)
+{
+	const char *line = buffer_read_line(&report_buffer);
+	if (line)
+		return line;
+	if (buffer_ferror(&report_buffer))
+		die_errno("error reading from fast-import");
+	die("unexpected end of fast-import feedback");
+}
+
 void fast_export_blob(uint32_t mode, uint32_t mark, uint32_t len, struct line_buffer *input)
 {
 	if (mode == REPO_MODE_LNK) {

vcs-svn/fast_export.h

@@ -3,6 +3,10 @@
 
 #include "line_buffer.h"
 
+void fast_export_init(int fd);
+void fast_export_deinit(void);
+void fast_export_reset(void);
+
 void fast_export_delete(uint32_t depth, uint32_t *path);
 void fast_export_modify(uint32_t depth, uint32_t *path, uint32_t mode,
 			uint32_t mark);