allow filtering by albumartist

keys are "albumartist" (long) and "~A" (short)

Doc/cmus.txt

@@ -1144,13 +1144,13 @@ built-in filters. Also (and)-grouping is done implicitly.
 @h2 Strings
 
 @li long
-*filename*, *artist*, *album*, *title*, *genre*, *comment*, *codec*,
-*codec_profile*
+*filename*, *artist*, *albumartist*, *album*, *title*, *genre*, *comment*,
+*codec*, *codec_profile*
 @br
 Comparators: *=* and *!=* (not equal)
 
 @li short
-*~f*, *~a*, *~l*, *~t*, *~g*, *~c*
+*~f*, *~a*, *~A*, *~l*, *~t*, *~g*, *~c*
 @br
 Comparators: none
 

expr.c

@@ -402,6 +402,7 @@ static const struct {
 	char short_key;
 	const char *long_key;
 } map_short2long[] = {
+	{ 'A',	"albumartist"	},
 	{ 'D',	"discnumber"	},
 	{ 'T',	"tag",		},
 	{ 'a',	"artist"	},
@@ -422,6 +423,7 @@ static const struct {
 	enum expr_type type;
 } builtin[] = {
 	{ "album",	EXPR_STR	},
+	{ "albumartist",EXPR_STR	},
 	{ "artist",	EXPR_STR	},
 	{ "bitrate",	EXPR_INT	},
 	{ "codec",	EXPR_STR	},
@@ -831,7 +833,7 @@ unsigned int expr_get_match_type(struct expr *expr)
 	}
 
 	key = expr->key;
-	if (strcmp(key, "artist") == 0)
+	if (strcmp(key, "artist") == 0 || strcmp(key, "albumartist") == 0)
 		return TI_MATCH_ARTIST;
 	if (strcmp(key, "album") == 0 || strcmp(key, "discnumber") == 0)
 		return TI_MATCH_ALBUM;