refactor: use specific error type for rev_parse_single()

Author: Byron

git-repository/src/repository/revision.rs

@@ -2,7 +2,7 @@ use crate::{bstr::BStr, revision, Id};
 
 /// Methods for resolving revisions by spec or working with the commit graph.
 impl crate::Repository {
-    /// Parse a revision specification and turn it into the full id to the object it describes, similar to `git rev-parse`.
+    /// Parse a revision specification and turn it into the object(s) it describes, similar to `git rev-parse`.
     pub fn rev_parse<'a>(&self, spec: impl Into<&'a BStr>) -> Result<revision::Spec<'_>, revision::spec::parse::Error> {
         revision::Spec::from_bstr(
             spec,
@@ -14,15 +14,15 @@ impl crate::Repository {
         )
     }
 
-    /// Parse a revision specification and return a Result containing the single included object
-    /// represented by this instance, or `Err` if it is a range of any kind.
+    /// Parse a revision specification and return single object id as represented by this instance.
     pub fn rev_parse_single<'repo, 'a>(
         &'repo self,
         spec: impl Into<&'a BStr>,
-    ) -> Result<Id<'repo>, revision::spec::parse::Error> {
+    ) -> Result<Id<'repo>, revision::spec::parse::single::Error> {
+        let spec = spec.into();
         self.rev_parse(spec)?
             .single()
-            .ok_or(revision::spec::parse::Error::SingleNotFound)
+            .ok_or(revision::spec::parse::single::Error::RangedRev { spec: spec.into() })
     }
 
     /// Create the baseline for a revision walk by initializing it with the `tips` to start iterating on.

git-repository/src/revision/spec/parse/mod.rs

@@ -8,6 +8,21 @@ use crate::{bstr::BStr, revision::Spec, Repository};
 mod types;
 pub use types::{Error, ObjectKindHint, Options, RefsHint};
 
+///
+pub mod single {
+    use crate::bstr::BString;
+
+    /// The error returned by [`crate::Repository::rev_parse_single()`].
+    #[derive(Debug, thiserror::Error)]
+    #[allow(missing_docs)]
+    pub enum Error {
+        #[error(transparent)]
+        Parse(#[from] super::Error),
+        #[error("revspec {spec:?} did not resolve to a single object")]
+        RangedRev { spec: BString },
+    }
+}
+
 ///
 pub mod error;