[repository #164] another test and fix for commit()

git-repository/src/easy/ext/object.rs

@@ -86,7 +86,7 @@ pub trait ObjectAccessExt: easy::Access + Sized {
     ///
     /// `reference` will be created if it doesn't exist, and can be `"HEAD"` to automatically write-through to the symbolic reference
     /// that `HEAD` points to if it is not detached. For this reason, detached head states cannot be created unless the `HEAD` is detached
-    /// already.
+    /// already. The reflog will be written as canonical git would do, like `<operation> (<detail>): <summary>`.
     ///
     /// The first parent id in `parents` is expected to be the current target of `reference` and the operation will fail if it is not.
     /// If there is no parent, the `reference` is expected to not exist yet.
@@ -137,7 +137,13 @@ pub trait ObjectAccessExt: easy::Access + Sized {
                         message: crate::reference::log::message("commit", &commit),
                     },
                     expected: match commit.parents.get(0).map(|p| Target::Peeled(*p)) {
-                        Some(previous) => PreviousValue::ExistingMustMatch(previous),
+                        Some(previous) => {
+                            if reference.as_bstr() == "HEAD" {
+                                PreviousValue::MustExistAndMatch(previous)
+                            } else {
+                                PreviousValue::ExistingMustMatch(previous)
+                            }
+                        }
                         None => PreviousValue::MustNotExist,
                     },
                     new: Target::Peeled(commit_id.inner),

git-repository/tests/easy/ext/object.rs

@@ -19,6 +19,24 @@ mod commit {
     use git_repository as git;
     use git_repository::prelude::{ObjectAccessExt, ReferenceAccessExt};
     use git_testtools::hex_to_id;
+    #[test]
+    fn parent_in_initial_commit_causes_failure() {
+        let tmp = tempfile::tempdir().unwrap();
+        let repo = git::init(&tmp).unwrap().into_easy();
+        let empty_tree_id = repo.write_object(&git::objs::Tree::empty()).unwrap().detach();
+        let author = git::actor::Signature::empty();
+        let err = repo
+            .commit(
+                "HEAD",
+                &author.to_ref(),
+                &author.to_ref(),
+                "initial",
+                empty_tree_id,
+                [empty_tree_id],
+            )
+            .unwrap_err();
+        assert_eq!(err.to_string(), "Reference 'refs/heads/main' was supposed to exist with value 4b825dc642cb6eb9a060e54bf8d69288fbee4904, but didn't.", "cannot provide parent id in initial commit");
+    }
 
     #[test]
     fn single_line_initial_commit_empty_tree_ref_nonexisting() -> crate::Result {
@@ -41,6 +59,7 @@ mod commit {
         );
 
         let head = repo.head()?.into_referent();
+        assert_eq!(head.name().as_bstr(), "refs/heads/main", "'main' is the default name");
         assert_eq!(
             head.log()?
                 .iter_rev()?