fix: Avoid duplicate signoff with stgit.autosign

With stgit.autosign configured, duplicate Signed-off-by trailers would
added when refreshing a patch. In the Python implementation, the
stgit.autosign configuration only affected `stg new` and `stg import`, so
the fix is to use that same policy.

N.B. also considered was to use the --if-exists=addIfDifferent option with
`git interpret-trailers`. This option would work to avoid duplicate
trailers, but may still cause trailers to be added unexpectedly when
running commands such as `stg refresh`, `stg edit`, `stg pick`, etc.

Fixes: #227

Author: jpgrayson

src/cmd/import.rs

@@ -640,6 +640,7 @@ fn create_patch<'repo>(
         .override_parent_id(stack.branch_head.id())
         .default_author(author)
         .default_message(message)
+        .allow_autosign(true)
         .allow_implicit_edit(false)
         .allow_diff_edit(true)
         .allow_template_save(false)

src/cmd/new.rs

@@ -193,6 +193,7 @@ fn run(matches: &ArgMatches) -> Result<()> {
     let parent_id = stack.branch_head.id();
 
     let (patchname, commit_id) = match patchedit::EditBuilder::default()
+        .allow_autosign(true)
         .allow_diff_edit(false)
         .allow_implicit_edit(true)
         .allow_template_save(!is_refreshing)

src/patchedit/mod.rs

@@ -306,13 +306,23 @@ pub(crate) struct EditBuilder<'a, 'repo> {
     template_patchname: Option<Option<PatchName>>,
     allowed_patchnames: Vec<PatchName>,
     patch_commit: Option<&'a git2::Commit<'repo>>,
+    allow_autosign: bool,
     allow_diff_edit: bool,
     allow_implicit_edit: bool,
     allow_template_save: bool,
     overlay: Overlay,
 }
 
 impl<'a, 'repo> EditBuilder<'a, 'repo> {
+    /// Set whether the autosign configuration should be used.
+    ///
+    /// When true, the `stgit.autosign` configuration will be used to determine whether
+    /// the configured trailer is automatically added to the message.
+    pub(crate) fn allow_autosign(mut self, allow: bool) -> Self {
+        self.allow_autosign = allow;
+        self
+    }
+
     /// Set whether the user is allowed/instructed to edit the diff content.
     ///
     /// When true, if the user makes any modifications to the diff content in an
@@ -444,6 +454,7 @@ impl<'a, 'repo> EditBuilder<'a, 'repo> {
             template_patchname,
             allowed_patchnames,
             patch_commit,
+            allow_autosign,
             allow_diff_edit,
             allow_implicit_edit,
             allow_template_save,
@@ -562,7 +573,11 @@ impl<'a, 'repo> EditBuilder<'a, 'repo> {
         };
 
         let message = {
-            let autosign = config.get_string("stgit.autosign").ok();
+            let autosign = if allow_autosign {
+                config.get_string("stgit.autosign").ok()
+            } else {
+                None
+            };
             // N.B. add_trailers needs to operate on utf-8 data. The user providing
             // trailer-altering options (e.g. --review) will force the message to be
             // decoded. In such cases the returned message will wrap a utf-8 String.

t/t1003-new.sh

@@ -144,6 +144,16 @@ test_expect_success \
     git cat-file -p HEAD | grep -e "Signed-off-by: C Ó Mitter <[email protected]>"
 '
 
+test_expect_success \
+    'Ensure autosign does not duplicate sign-off' '
+    test_config stgit.autosign "Signed-off-by" &&
+    stg edit --ack &&
+    echo "more stuff" >> file.txt &&
+    stg refresh &&
+    git cat-file -p HEAD | grep -e "Signed-off-by:" >out &&
+    test_line_count = 1 out
+'
+
 test_expect_success \
     'Patch with slash in name' '
     general_error stg new bar/foo -m "patch bar/foo"