feat(record): add --before flag to insert commit before current HEAD

git-branchless-lib/src/core/rewrite/execute.rs

@@ -327,6 +327,10 @@ pub enum MergeConflictRemediation {
 
     /// Indicate that the user should run `git move -m -s 'siblings(.)'`.
     Insert,
+
+    // TODO: confirm this message
+    /// Indicate that the user should run `git move -m -x HEAD~ --onto HEAD`.
+    Before,
 }
 
 /// Information about a failure to merge that occurred while moving commits.
@@ -415,6 +419,12 @@ impl FailedMergeInfo {
                     "To resolve merge conflicts, run: git move -m -s 'siblings(.)'"
                 )?;
             }
+            MergeConflictRemediation::Before => {
+                writeln!(
+                    effects.get_output_stream(),
+                    "To resolve merge conflicts, run: git move -m -x HEAD~ --onto HEAD"
+                )?;
+            }
         }
 
         Ok(())

git-branchless-opts/src/lib.rs

@@ -347,6 +347,11 @@ pub struct RecordArgs {
     #[clap(action, short = 'I', long = "insert")]
     pub insert: bool,
 
+    /// Insert the new commit before HEAD, as a child of HEAD~, then rebase
+    /// HEAD onto the new commit.
+    #[clap(action, long = "before", conflicts_with("insert"))]
+    pub before: bool,
+
     /// After making the new commit, switch back to the previous commit.
     #[clap(action, short = 's', long = "stash", conflicts_with_all(&["create", "detach"]))]
     pub stash: bool,