convert.c: ident + core.autocrlf didn't work

When the ident attributes is set, get_stream_filter() did not obey
core.autocrlf=true, and the file was checked out with LF.

Change the rule when a streaming filter can be used:
- if an external filter is specified, don't use a stream filter.
- if the worktree eol is CRLF and "auto" is active, don't use a stream filter.
- Otherwise the stream filter can be used.

Add test cases in t0027.

Signed-off-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

convert.c

@@ -1380,27 +1380,22 @@ static struct stream_filter *ident_filter(const unsigned char *sha1)
 struct stream_filter *get_stream_filter(const char *path, const unsigned char *sha1)
 {
 	struct conv_attrs ca;
-	enum crlf_action crlf_action;
 	struct stream_filter *filter = NULL;
 
 	convert_attrs(&ca, path);
-
 	if (ca.drv && (ca.drv->smudge || ca.drv->clean))
-		return filter;
+		return NULL;
+
+	if (ca.crlf_action == CRLF_AUTO || ca.crlf_action == CRLF_AUTO_CRLF)
+		return NULL;
 
 	if (ca.ident)
 		filter = ident_filter(sha1);
 
-	crlf_action = ca.crlf_action;
+	if (output_eol(ca.crlf_action) == EOL_CRLF)
-
-	if ((crlf_action == CRLF_BINARY) ||
-			crlf_action == CRLF_AUTO_INPUT ||
-			(crlf_action == CRLF_TEXT_INPUT))
-		filter = cascade_filter(filter, &null_filter_singleton);
-
-	else if (output_eol(crlf_action) == EOL_CRLF &&
-		 !(crlf_action == CRLF_AUTO || crlf_action == CRLF_AUTO_CRLF))
 		filter = cascade_filter(filter, lf_to_crlf_filter());
+	else
+		filter = cascade_filter(filter, &null_filter_singleton);
 
 	return filter;
 }

t/t0027-auto-crlf.sh

@@ -493,7 +493,7 @@ fi
 export CRLF_MIX_LF_CR MIX NL
 
 # Same handling with and without ident
-for id in ""
+for id in "" ident
 do
 	for ceol in lf crlf native
 	do