refactor

- more possible inputs for '@' in branches
- assure ranges are also handled
- remove error variant which should not be possible anymore

Co-authored-by: Thomas Letan <lthms@soap.coffee>
Co-authored-by: Sebastian Thiel <sebastian.thiel@icloud.com>

Author: Byron

gix-revision/src/spec/parse/function.rs

@@ -344,15 +344,19 @@ where
     {
         let mut cursor = input;
         let mut ofs = 0;
+        const SEPARATORS: &[u8] = b"~^:.";
         while let Some((pos, b)) = cursor.iter().enumerate().find(|(pos, b)| {
             if **b == b'@' {
-                cursor.get(pos + 1) == Some(&b'{')
-                    || cursor
-                        .get(pos + 1)
-                        .and_then(|b| Some(b"~^:.".contains(b)))
-                        .unwrap_or(false)
-                    || (*pos == 0 && cursor.get(1) == None)
-            } else if b"~^:.".contains(b) {
+                if cursor.len() == 1 {
+                    return true;
+                }
+                let next = cursor.get(pos + 1);
+                let next_next = cursor.get(pos + 2);
+                if *pos != 0 && (next, next_next) == (Some(&b'.'), Some(&b'.')) {
+                    return false;
+                }
+                next == Some(&b'{') || next.map_or(false, |b| SEPARATORS.contains(b))
+            } else if SEPARATORS.contains(b) {
                 true
             } else {
                 if let Some(num) = consecutive_hex_chars.as_mut() {

gix-revision/tests/spec/parse/anchor/refnames.rs

@@ -1,5 +1,3 @@
-use gix_revision::spec;
-
 use crate::spec::parse::{parse, try_parse};
 
 #[test]
@@ -11,9 +9,36 @@ fn at_by_itself_is_shortcut_for_head() {
 
 #[test]
 fn at_is_allowed() {
-    let rec = parse("a@b");
-    assert!(rec.kind.is_none());
-    assert_eq!(rec.get_ref(0), "a@b");
+    for name in ["a@b", "@branch", "branch@", "@@", "@inner@"] {
+        let rec = parse(name);
+        assert!(rec.kind.is_none());
+        assert_eq!(rec.get_ref(0), name);
+        assert_eq!(rec.find_ref[1], None);
+    }
+}
+
+#[test]
+fn at_in_ranges_is_allowed() {
+    let input = "@@@..";
+    let rec = parse(input);
+    assert_eq!(rec.kind, Some(gix_revision::spec::Kind::RangeBetween));
+    assert_eq!(rec.get_ref(0), "@@@");
+    assert_eq!(rec.get_ref(1), "HEAD");
+
+    let input = "@@...@@";
+    let rec = parse(input);
+    assert_eq!(rec.kind, Some(gix_revision::spec::Kind::ReachableToMergeBase));
+    assert_eq!(rec.get_ref(0), "@@");
+    assert_eq!(rec.get_ref(1), "@@");
+}
+
+#[test]
+fn strange_revspecs_do_not_panic() {
+    let err = try_parse(".@.").unwrap_err();
+    assert!(matches!(
+        err,
+        gix_revision::spec::parse::Error::AtNeedsCurlyBrackets { input } if input == "@."
+    ));
 }
 
 #[test]