Implement the in-process structured entry editor

Closes #21

crates/storage/src/git.rs

@@ -25,7 +25,7 @@ use crate::{
     mutation::{TreeCommit, TreeCommitError, TreeCommitter},
     recipient::{PolicyCommit, PolicyCommitError, PolicyCommitter},
     repository::{EncryptedEntry, Repository, SecretBytes},
-    write::{EntryCommit, EntryCommitError, EntryCommitter},
+    write::{EntryCommit, EntryCommitError, EntryCommitter, NoGitEntryCommitter},
 };
 
 const DEFAULT_BRANCH: &str = "main";
@@ -38,6 +38,11 @@ pub struct GitIdentity {
 }
 
 impl GitIdentity {
+    pub fn ironstorage() -> Self {
+        Self::new("IronStorage", "ironstorage@localhost")
+            .expect("the built-in Git identity is valid")
+    }
+
     pub fn new(name: impl Into<String>, email: impl Into<String>) -> Result<Self, GitError> {
         let name = name.into();
         let email = email.into();
@@ -257,6 +262,35 @@ pub struct GitRepository {
     identity: GitIdentity,
 }
 
+/// Storage-owned selection of pass-compatible automatic Git commits.
+pub enum AutomaticEntryCommitter {
+    Git(Box<GitRepository>),
+    None(NoGitEntryCommitter),
+}
+
+impl AutomaticEntryCommitter {
+    pub fn for_entry(
+        repository: &Repository,
+        entry: &str,
+        identity: GitIdentity,
+    ) -> Result<Self, GitError> {
+        match GitRepository::open_innermost(repository, Path::new(entry), identity) {
+            Ok(git) => Ok(Self::Git(Box::new(git))),
+            Err(GitError::NotRepository) => Ok(Self::None(NoGitEntryCommitter)),
+            Err(error) => Err(error),
+        }
+    }
+}
+
+impl EntryCommitter for AutomaticEntryCommitter {
+    fn commit(&mut self, change: &EntryCommit) -> Result<(), EntryCommitError> {
+        match self {
+            Self::Git(git) => EntryCommitter::commit(git.as_mut(), change),
+            Self::None(committer) => committer.commit(change),
+        }
+    }
+}
+
 pub struct GitCredential {
     username: String,
     password: crate::repository::SecretBytes,