[PATCH v1] hash: handle invalid algorithms when formatting object IDs

[shrimech <eddinen77@gmail.com>]

ObjectID::algo is publicly mutable, so an ObjectID may contain an algorithm
identifier that is not recognized by HashAlgorithm. Display previously
unwrapped as_slice(), which returns an error for such identifiers, causing
formatting to panic.

Format the full hash storage for invalid identifiers and append an
invalid-hash-algo marker containing the unsupported identifier. Add a
regression test covering this case while preserving the existing output for
valid algorithms.

Signed-off-by: shrimech <eddinen77@gmail.com>
---

Notes:
    Base Ref: v2.56.0
    Web-Diff: https://github.com/larsxschneider/git/commit/c95530cf38
    Checkout: git fetch https://github.com/larsxschneider/git fix/objectid-display-invalid-algo-v1 && git checkout c95530cf38

 src/hash.rs | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/src/hash.rs b/src/hash.rs
index e1f2d31fc3..87242d58b1 100644
--- a/src/hash.rs
+++ b/src/hash.rs
@@ -78,13 +78,19 @@ impl ObjectID {
 }
 
 impl Display for ObjectID {
-    /// Format this object ID as a hex object ID.
+    /// Format this object ID as a hex object ID, or mark it if its algorithm is invalid.
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let hash = self.as_slice().unwrap();
+        let hash = match self.as_slice() {
+            Ok(hash) => hash,
+            Err(_) => &self.hash,
+        };
         for x in hash {
             write!(f, "{:02x}", x)?;
         }
-        Ok(())
+        match self.algo() {
+            Ok(_) => Ok(()),
+            Err(e) => write!(f, ":invalid-hash-algo-{}", e.0),
+        }
     }
 }
 
@@ -366,7 +372,7 @@ pub mod c {
 
 #[cfg(test)]
 mod tests {
-    use super::{CryptoDigest, HashAlgorithm, ObjectID};
+    use super::{CryptoDigest, HashAlgorithm, ObjectID, GIT_MAX_RAWSZ};
     use std::io::Write;
 
     fn all_algos() -> &'static [HashAlgorithm] {
@@ -439,6 +445,19 @@ mod tests {
         }
     }
 
+    #[test]
+    fn invalid_object_ids_format_without_panicking() {
+        let oid = ObjectID {
+            hash: [0xab; GIT_MAX_RAWSZ],
+            algo: 0,
+        };
+
+        assert_eq!(
+            format!("{}", oid),
+            format!("{}:invalid-hash-algo-0", "ab".repeat(GIT_MAX_RAWSZ))
+        );
+    }
+
     #[test]
     fn hasher_works_correctly() {
         for algo in all_algos() {

base-commit: a018953688f1b10bddf91bff8747068f5f4746a4
-- 
2.47.3