parse: Ignore -- on the command line.

find uses -- to indicate the end of the flags.  That is,

    $ find -L -- -type f

is allowed, but

    $ find -- -L -type f

results in an error about an unknown predicate `-L`.  This behaviour
doesn't seem particularly useful -- in particular, unlike most other
tools, it doesn't help you if you want to specify a filename beginning
with a -.

So to ensure bfs is compatible with all GNU find command lines, we just
ignore -- whenever it appears.

2 files changed, 32 insertions, 6 deletions

diff --git a/parse.c b/parse.c
index 6d55317..6a4dfc6 100644
--- a/parse.c
+++ b/parse.c
@@ -327,18 +327,33 @@ static bool parse_root(struct parser_state *state, const char *path) {
 static const char *skip_paths(struct parser_state *state) {
 	while (true) {
 		const char *arg = state->argv[0];
+		if (!arg) {
+			return NULL;
+		}
+
+		if (arg[0] == '-') {
+			if (strcmp(arg, "--") == 0) {
+				// find uses -- to separate flags from the rest
+				// of the command line.  We allow mixing flags
+				// and paths/predicates, so we just ignore --.
+				parser_advance(state, T_FLAG, 1);
+				continue;
+			}
+			if (strcmp(arg, "-") != 0) {
+				// - by itself is a file name.  Anything else
+				// starting with - is a flag/predicate.
+				return arg;
+			}
+		}
 
 		// By POSIX, these are always options
-		if (!arg
-		    || (arg[0] == '-' && arg[1])
-		    || strcmp(arg, "(") == 0
-		    || strcmp(arg, "!") == 0) {
+		if (strcmp(arg, "(") == 0 || strcmp(arg, "!") == 0) {
 			return arg;
 		}
 
 		if (state->expr_started) {
 			// By POSIX, these can be paths.  We only treat them as
-			// such at the beginning of the command line
+			// such at the beginning of the command line.
 			if (strcmp(arg, ")") == 0 || strcmp(arg, ",") == 0) {
 				return arg;
 			}
@@ -1467,6 +1482,7 @@ static const struct table_entry parse_table[] = {
 	{"writable", false, parse_access, W_OK},
 	{"xdev", false, parse_mount},
 	{"xtype", false, parse_type, true},
+	{"-"},
 	{"-help", false, parse_help},
 	{"-version", false, parse_version},
 	{0},
diff --git a/tests.sh b/tests.sh
index 5fd4a9b..63de3ee 100755
--- a/tests.sh
+++ b/tests.sh
@@ -367,7 +367,17 @@ function test_0065() {
     diff -u "$out/out.find" "$out/out.bfs"
 }
 
-for i in {1..65}; do
+function test_0066() {
+    cd "$basic"
+    find_diff -- -type f
+}
+
+function test_0067() {
+    cd "$basic"
+    find_diff -L -- -type f
+}
+
+for i in {1..67}; do
     test="test_$(printf '%04d' $i)"
     ("$test" "$dir")
     status=$?