Add forceDetach configuration option to always bypass detached HEAD check

Author: blairconrad

Documentation/git-absorb.adoc

@@ -190,6 +190,18 @@ edit your local or global `.gitconfig` and add the following section:
     forceAuthor = true
 .............................................................................
 
+GENERATE FIXUPS ON DETACHED HEAD
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+By default, git-absorb will not generate fixup commits when HEAD is not a
+branch ("is detached"). To always generate fixups on detached HEADs,
+edit your local or global `.gitconfig` and add the following section:
+
+.............................................................................
+[absorb]
+    forceDetach = true
+.............................................................................
+
 GITHUB PROJECT
 --------------
 

src/config.rs

@@ -7,6 +7,9 @@ pub const MAX_STACK: usize = 10;
 pub const FORCE_AUTHOR_CONFIG_NAME: &str = "absorb.forceAuthor";
 pub const FORCE_AUTHOR_DEFAULT: bool = false;
 
+pub const FORCE_DETACH_CONFIG_NAME: &str = "absorb.forceDetach";
+pub const FORCE_DETACH_DEFAULT: bool = false;
+
 pub const ONE_FIXUP_PER_COMMIT_CONFIG_NAME: &str = "absorb.oneFixupPerCommit";
 pub const ONE_FIXUP_PER_COMMIT_DEFAULT: bool = false;
 
@@ -36,7 +39,9 @@ pub fn unify<'config>(config: &'config Config, repo: &Repository) -> Config<'con
         force_author: config.force_author
             || config.force
             || bool_value(&repo, FORCE_AUTHOR_CONFIG_NAME, FORCE_AUTHOR_DEFAULT),
-        force_detach: config.force_detach || config.force,
+        force_detach: config.force_detach
+            || config.force
+            || bool_value(&repo, FORCE_DETACH_CONFIG_NAME, FORCE_DETACH_DEFAULT),
         ..*config
     }
 }

src/lib.rs

@@ -594,11 +594,7 @@ mod tests {
 
         repo_utils::become_new_author(&ctx);
 
-        ctx.repo
-            .config()
-            .unwrap()
-            .set_str("absorb.forceAuthor", "true")
-            .unwrap();
+        repo_utils::set_config_flag(&ctx.repo, "absorb.forceAuthor");
 
         // run 'git-absorb'
         let drain = slog::Discard;
@@ -696,6 +692,25 @@ mod tests {
         assert!(nothing_left_in_index(&ctx.repo).unwrap());
     }
 
+    #[test]
+    fn detached_head_with_force_detach_config() {
+        let ctx = repo_utils::prepare_and_stage();
+        repo_utils::detach_head(&ctx);
+        repo_utils::delete_branch(&ctx.repo, "master");
+
+        repo_utils::set_config_flag(&ctx.repo, "absorb.forceDetach");
+
+        // run 'git-absorb'
+        let drain = slog::Discard;
+        let logger = slog::Logger::root(drain, o!());
+        run_with_repo(&logger, &DEFAULT_CONFIG, &ctx.repo).unwrap();
+        let mut revwalk = ctx.repo.revwalk().unwrap();
+        revwalk.push_head().unwrap();
+
+        assert_eq!(revwalk.count(), 3);
+        assert!(nothing_left_in_index(&ctx.repo).unwrap());
+    }
+
     #[test]
     fn attached_head_pointing_at_commit_on_a_second_branch() {
         let ctx = repo_utils::prepare_and_stage();

src/tests/repo_utils.rs

@@ -104,3 +104,8 @@ pub fn delete_branch(repo: &git2::Repository, branch_name: &str) {
         .unwrap();
     branch.delete().unwrap();
 }
+
+/// Set the named repository config flag to true.
+pub fn set_config_flag(repo: &git2::Repository, flag_name: &str) {
+    repo.config().unwrap().set_str(flag_name, "true").unwrap();
+}