Avoid panic when re-locking with precise commit (#5863)

## Summary

Very subtle bug. The scenario is as follows:

- We resolve: `elmer-circuitbuilder = { git =
"https://github.com/ElmerCSC/elmer_circuitbuilder.git" }`

- The user then changes the request to: `elmer-circuitbuilder = { git =
"https://github.com/ElmerCSC/elmer_circuitbuilder.git", rev =
"44d2f4b19d6837ea990c16f494bdf7543d57483d" }`

- When we go to re-lock, we note two facts:

1. The "default branch" resolves to
`44d2f4b19d6837ea990c16f494bdf7543d57483d`.
2. The metadata for `44d2f4b19d6837ea990c16f494bdf7543d57483d` is
(whatever we grab from the lockfile).

- In the resolver, we then ask for the metadata for
`44d2f4b19d6837ea990c16f494bdf7543d57483d`. It's already in the cache,
so we return it; thus, we never add the
`44d2f4b19d6837ea990c16f494bdf7543d57483d` ->
`44d2f4b19d6837ea990c16f494bdf7543d57483d` mapping to the Git resolver,
because we never have to resolve it.

This would apply for any case in which a requested tag or branch was
replaced by its precise SHA. Replacing with a different commit is fine.

It only applied to `tool.uv.sources`, and not PEP 508 URLs, because the
underlying issue is that we aren't consistent about "automatically"
extracting the precise commit from a Git reference.

Closes https://github.com/astral-sh/uv/issues/5860.

crates/pypi-types/src/parsed_url.rs

@@ -246,10 +246,11 @@ impl ParsedGitUrl {
         precise: Option<GitSha>,
         subdirectory: Option<PathBuf>,
     ) -> Self {
-        let mut url = GitUrl::new(repository, reference);
-        if let Some(precise) = precise {
-            url = url.with_precise(precise);
-        }
+        let url = if let Some(precise) = precise {
+            GitUrl::from_commit(repository, reference, precise)
+        } else {
+            GitUrl::from_reference(repository, reference)
+        };
         Self { url, subdirectory }
     }
 }

crates/pypi-types/src/requirement.rs

@@ -113,9 +113,9 @@ impl From<Requirement> for pep508_rs::Requirement<VerbatimParsedUrl> {
                     url,
                 } => {
                     let git_url = if let Some(precise) = precise {
-                        GitUrl::new(repository, reference).with_precise(precise)
+                        GitUrl::from_commit(repository, reference, precise)
                     } else {
-                        GitUrl::new(repository, reference)
+                        GitUrl::from_reference(repository, reference)
                     };
                     Some(VersionOrUrl::Url(VerbatimParsedUrl {
                         parsed_url: ParsedUrl::Git(ParsedGitUrl {