[PATCH 4/7] fast-import: Allow cat requests at arbitrary points in stream

[David Barr <david.barr@cordelta.com>]

From: Jonathan Nieder <jrnieder@gmail.com>

Rather than planning in advance and saving up a bunch of objects
before a "commit" command, frontends might want to wait until the
middle of a commit and request objects then.

Allow them to.

The new rule: a "cat" request can be inserted wherever a comment
is allowed, which means at the start of any line except in the
middle of a "data" command.

Cc: Ramkumar Ramachandra <artagnon@gmail.com>
Cc: David Barr <david.barr@cordelta.com>
Cc: Sverre Rabbelier <srabbelier@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
---
 Documentation/git-fast-import.txt |    4 ++
 fast-import.c                     |   27 ++++++++------
 t/t9300-fast-import.sh            |   72 +++++++++++++++++++++++++++++++++++++
 3 files changed, 92 insertions(+), 11 deletions(-)

diff --git a/Documentation/git-fast-import.txt b/Documentation/git-fast-import.txt
index 2cf48f5..b670c7d 100644
--- a/Documentation/git-fast-import.txt
+++ b/Documentation/git-fast-import.txt
@@ -920,6 +920,10 @@ a path within that tree to retrieve a subtree or blob.
 A `<path>` string should be surrounded with quotation marks and
 use C-style escaping.
 
+The `cat` command can be used anywhere that comments are
+acceptable.  In particular, the `cat` command can be used in the
+middle of a commit, but not in the middle of a `data` stream.
+
 `feature`
 ~~~~~~~~~
 Require that fast-import supports the specified feature, or abort if
diff --git a/fast-import.c b/fast-import.c
index f3c4123..87246d5 100644
--- a/fast-import.c
+++ b/fast-import.c
@@ -55,9 +55,6 @@ Format of STDIN stream:
     ('from' sp committish lf)?
     lf?;
 
-  cat_request ::= 'cat' sp (hexsha1 | idnum) lf
-    | 'cat' sp hexsha1 sp path_str lf;
-
   checkpoint ::= 'checkpoint' lf
     lf?;
 
@@ -135,14 +132,18 @@ Format of STDIN stream:
   ts    ::= # time since the epoch in seconds, ascii base10 notation;
   tz    ::= # GIT style timezone;
 
-     # note: comments may appear anywhere in the input, except
-     # within a data command.  Any form of the data command
-     # always escapes the related input from comment processing.
+     # note: comments and cat requests may appear anywhere
+     # in the input, except within a data command.  Any form
+     # of the data command always escapes the related input
+     # from comment processing.
      #
      # In case it is not clear, the '#' that starts the comment
      # must be the first character on that line (an lf
      # preceded it).
      #
+  cat_request ::= 'cat' sp (hexsha1 | idnum) lf
+    | 'cat' sp hexsha1 sp path_str lf;
+
   comment ::= '#' not_lf* lf;
   not_lf  ::= # Any byte that is not ASCII newline (LF);
 */
@@ -368,6 +369,7 @@ static int seen_data_command;
 static int report_fd = -1;
 
 static void parse_argv(void);
+static void parse_cat_request(void);
 
 static void write_branch_report(FILE *rpt, struct branch *b)
 {
@@ -1777,7 +1779,6 @@ static void read_marks(void)
 	fclose(f);
 }
 
-
 static int read_next_command(void)
 {
 	static int stdin_eof = 0;
@@ -1787,7 +1788,7 @@ static int read_next_command(void)
 		return EOF;
 	}
 
-	do {
+	for (;;) {
 		if (unread_command_buf) {
 			unread_command_buf = 0;
 		} else {
@@ -1820,7 +1821,13 @@ static int read_next_command(void)
 			rc->prev->next = rc;
 			cmd_tail = rc;
 		}
-	} while (command_buf.buf[0] == '#');
+		if (!prefixcmp(command_buf.buf, "cat ")) {
+			parse_cat_request();
+			continue;
+		}
+		if (command_buf.buf[0] != '#')
+			return 0;
+	}
 
 	return 0;
 }
@@ -3081,8 +3088,6 @@ int main(int argc, const char **argv)
 			parse_new_tag();
 		else if (!prefixcmp(command_buf.buf, "reset "))
 			parse_reset_branch();
-		else if (!prefixcmp(command_buf.buf, "cat "))
-			parse_cat_request();
 		else if (!strcmp("checkpoint", command_buf.buf))
 			parse_checkpoint();
 		else if (!prefixcmp(command_buf.buf, "progress "))
diff --git a/t/t9300-fast-import.sh b/t/t9300-fast-import.sh
index 8155b85..a85d068 100755
--- a/t/t9300-fast-import.sh
+++ b/t/t9300-fast-import.sh
@@ -1749,6 +1749,78 @@ test_expect_success PIPE 'R: report-fd: can feed back printed blob' '
 	compare_diff_raw expect actual
 '
 
+test_expect_success PIPE 'R: report-fd: cat commands mid-commit' '
+	file4_id=$(
+		printf "%s" "$file4_data" |
+		git hash-object --stdin
+	) &&
+	cat >expect <<-EOF &&
+	:100755 100644 $file4_id $file4_id C100 file4	file4-copy
+	EOF
+	git cat-file commit refs/heads/branch >expect.commit &&
+	echo tree >expect.type &&
+	git cat-file tree refs/heads/branch >expect.tree &&
+
+	cat >frontend <<-\FRONTEND_END &&
+	#!/bin/sh
+
+	branch=$(git rev-parse --verify refs/heads/branch) &&
+	cat <<EOF &&
+	feature report-fd=3
+	commit refs/heads/catdemo
+	cat $branch
+	EOF
+
+	read commit_id type size <&3 &&
+	dd if=/dev/stdin of=commit bs=1 count=$size <&3 &&
+	read newline <&3 &&
+	read tree tree_id <commit &&
+
+	echo "cat $tree_id" &&
+
+	read tree_id2 type size <&3 &&
+	dd if=/dev/stdin of=tree bs=1 count=$size <&3 &&
+	read newline <&3 &&
+	echo $type >type &&
+
+	grep ^committer commit &&
+	cat <<EOF &&
+	data <<COMMIT
+	copy file4 as file4-copy
+	COMMIT
+
+	from refs/heads/branch^0
+	cat $tree_id "file4"
+	EOF
+
+	read blob_id type size <&3 &&
+	dd if=/dev/stdin of=/dev/null bs=1 count=$size <&3 &&
+	read newline <&3 &&
+
+	cat <<EOF &&
+	M 644 $blob_id "file4-copy"
+	cat $tree_id ""
+
+	EOF
+
+	read tree_id3 type size <&3 &&
+	dd if=/dev/stdin of=tree2 bs=1 count=$size <&3 &&
+	read newline <&3 &&
+	read cid <&3
+	FRONTEND_END
+
+	mkfifo commits &&
+	test_when_finished "rm -f commits" &&
+	sh frontend 3<commits |
+	git fast-import 3>commits &&
+	git diff-tree -C catdemo^ catdemo >actual &&
+	compare_diff_raw expect actual
+	test_cmp expect.commit commit &&
+	test_cmp expect.type type &&
+	test_cmp expect.tree tree &&
+	test_cmp expect.tree tree2
+'
+
 cat >input << EOF
 option git quiet
 blob
-- 
1.7.3.1