Added some low- and high-level bindings for creating branches, settin… (#543)

* Added some low- and high-level bindings for creating branches, setting the repository HEAD, and getting reference names pointed to by annotated commits.

* Fixed rustfmt issue.

* Truly fix rustfmt issue.

Author: iancormac84

libgit2-sys/lib.rs

@@ -1806,6 +1806,10 @@ extern "C" {
         repo: *mut git_repository,
         commitish: *const git_oid,
     ) -> c_int;
+    pub fn git_repository_set_head_detached_from_annotated(
+        repo: *mut git_repository,
+        commitish: *const git_annotated_commit,
+    ) -> c_int;
     pub fn git_repository_set_bare(repo: *mut git_repository) -> c_int;
     pub fn git_repository_is_worktree(repo: *const git_repository) -> c_int;
     pub fn git_repository_is_bare(repo: *const git_repository) -> c_int;
@@ -2528,6 +2532,13 @@ extern "C" {
         target: *const git_commit,
         force: c_int,
     ) -> c_int;
+    pub fn git_branch_create_from_annotated(
+        ref_out: *mut *mut git_reference,
+        repository: *mut git_repository,
+        branch_name: *const c_char,
+        commit: *const git_annotated_commit,
+        force: c_int,
+    ) -> c_int;
     pub fn git_branch_delete(branch: *mut git_reference) -> c_int;
     pub fn git_branch_is_head(branch: *const git_reference) -> c_int;
     pub fn git_branch_iterator_free(iter: *mut git_branch_iterator);
@@ -2891,6 +2902,7 @@ extern "C" {
 
     // merge
     pub fn git_annotated_commit_id(commit: *const git_annotated_commit) -> *const git_oid;
+    pub fn git_annotated_commit_ref(commit: *const git_annotated_commit) -> *const c_char;
     pub fn git_annotated_commit_from_ref(
         out: *mut *mut git_annotated_commit,
         repo: *mut git_repository,

src/merge.rs

@@ -1,6 +1,7 @@
 use libc::c_uint;
 use std::marker;
 use std::mem;
+use std::str;
 
 use crate::call::Convert;
 use crate::util::Binding;
@@ -26,6 +27,18 @@ impl<'repo> AnnotatedCommit<'repo> {
     pub fn id(&self) -> Oid {
         unsafe { Binding::from_raw(raw::git_annotated_commit_id(self.raw)) }
     }
+
+    /// Get the refname that the given git_annotated_commit refers to
+    ///
+    /// Returns None if it is not valid utf8
+    pub fn refname(&self) -> Option<&str> {
+        str::from_utf8(self.refname_bytes()).ok()
+    }
+
+    /// Get the refname that the given git_annotated_commit refers to.
+    pub fn refname_bytes(&self) -> &[u8] {
+        unsafe { crate::opt_bytes(self, raw::git_annotated_commit_ref(&*self.raw)).unwrap() }
+    }
 }
 
 impl Default for MergeOptions {

src/repo.rs

@@ -742,6 +742,27 @@ impl Repository {
         Ok(())
     }
 
+    /// Make the repository HEAD directly point to the commit.
+    ///
+    /// If the provided committish cannot be found in the repository, the HEAD
+    /// is unaltered and an error is returned.
+    /// If the provided commitish cannot be peeled into a commit, the HEAD is
+    /// unaltered and an error is returned.
+    /// Otherwise, the HEAD will eventually be detached and will directly point
+    /// to the peeled commit.
+    pub fn set_head_detached_from_annotated(
+        &self,
+        commitish: AnnotatedCommit<'_>,
+    ) -> Result<(), Error> {
+        unsafe {
+            try_call!(raw::git_repository_set_head_detached_from_annotated(
+                self.raw,
+                commitish.raw()
+            ));
+        }
+        Ok(())
+    }
+
     /// Create an iterator for the repo's references
     pub fn references(&self) -> Result<References<'_>, Error> {
         let mut ret = ptr::null_mut();
@@ -1053,6 +1074,34 @@ impl Repository {
         }
     }
 
+    /// Create a new branch pointing at a target commit
+    ///
+    /// This behaves like `Repository::branch()` but takes
+    /// an annotated commit, which lets you specify which
+    /// extended sha syntax string was specified by a user,
+    /// allowing for more exact reflog messages.
+    ///
+    /// See the documentation for `Repository::branch()`
+    pub fn branch_from_annotated_commit(
+        &self,
+        branch_name: &str,
+        target: &AnnotatedCommit<'_>,
+        force: bool,
+    ) -> Result<Branch<'_>, Error> {
+        let branch_name = CString::new(branch_name)?;
+        let mut raw = ptr::null_mut();
+        unsafe {
+            try_call!(raw::git_branch_create_from_annotated(
+                &mut raw,
+                self.raw(),
+                branch_name,
+                target.raw(),
+                force
+            ));
+            Ok(Branch::wrap(Binding::from_raw(raw)))
+        }
+    }
+
     /// Lookup a branch by its name in a repository.
     pub fn find_branch(&self, name: &str, branch_type: BranchType) -> Result<Branch<'_>, Error> {
         let name = CString::new(name)?;