fabrica

hanna/fabrica

main
Switch branch
mainView all branches
Clone
HTTPS
SSH

feat(git): surface merge/rebase conflict details

c55d70c · hanna committed on 2026-07-25

MergeConflict now carries the conflicting paths (from merge-tree) or the rebase
output, and the PR merge error shows them, so a failed merge/rebase explains
itself instead of a bare "could not be merged cleanly". Add a diverged
non-conflicting merge/squash/rebase test (previously only fast-forward was
covered) confirming all three strategies succeed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed by hannaSSH key fingerprint: SHA256:4g9cWhkAAw8gwqhJUcVbSnGEvdGwklW+1Aa/fMUu59k
7 files changed · +76 −8UnifiedSplit
crates/git/src/lib.rs +4 −3
@@ -100,9 +100,10 @@ pub enum GitError {
100100 Merge(String),
101101
102102 /// A server-side merge could not apply cleanly: the three-way merge or the
103- /// rebase replay hit conflicts.
104- #[error("merge has conflicts")]
105- MergeConflict,
103+ /// rebase replay hit conflicts. The string names the conflicting paths (or
104+ /// the git output) when available.
105+ #[error("merge has conflicts: {0}")]
106+ MergeConflict(String),
106107
107108 /// `git init` (used for SHA-256 repositories) failed.
108109 #[error("git init failed: {0}")]
crates/git/src/merge.rs +65 −3
@@ -239,7 +239,13 @@ fn plumbing_commit(req: &MergeRequest, base: &str, parents: &[&str]) -> Result<S
239239 })?;
240240 match tree_out.status.code() {
241241 Some(0) => {}
242- Some(1) => return Err(GitError::MergeConflict),
242+ Some(1) => {
243+ // On a conflict, stdout is the (partial) tree oid followed by the
244+ // conflicted-file information; surface that as the detail.
245+ let out = String::from_utf8_lossy(&tree_out.stdout);
246+ let detail = out.lines().skip(1).collect::<Vec<_>>().join("; ");
247+ return Err(GitError::MergeConflict(detail.trim().to_string()));
248+ }
243249 _ => {
244250 return Err(GitError::Merge(
245251 String::from_utf8_lossy(&tree_out.stderr).trim().to_string(),
@@ -317,13 +323,19 @@ fn rebase_in_worktree(req: &MergeRequest, base: &str, head: &str) -> Result<Stri
317323 source,
318324 })?;
319325 if !out.status.success() {
326+ // Capture the reason before aborting (git prints it to stdout/stderr).
327+ let mut detail = String::from_utf8_lossy(&out.stdout).trim().to_string();
328+ let err = String::from_utf8_lossy(&out.stderr);
329+ if !err.trim().is_empty() {
330+ detail.push_str(err.trim());
331+ }
320332 // Leave no half-applied rebase state in the worktree.
321333 let _ = identified(req)
322334 .current_dir(req.workdir)
323335 .env_remove("GIT_DIR")
324336 .args(["rebase", "--abort"])
325337 .status();
326- return Err(GitError::MergeConflict);
338+ return Err(GitError::MergeConflict(detail));
327339 }
328340
329341 let tip = identified(req)
@@ -350,7 +362,7 @@ fn identified(req: &MergeRequest) -> Command {
350362
351363 #[cfg(test)]
352364 mod tests {
353- #![allow(clippy::unwrap_used, clippy::expect_used)]
365+ #![allow(clippy::unwrap_used, clippy::expect_used, clippy::panic)]
354366
355367 use std::path::{Path, PathBuf};
356368
@@ -457,6 +469,56 @@ mod tests {
457469 }
458470
459471 #[test]
472+ fn merge_and_rebase_diverged_non_conflicting() {
473+ if !git_present() {
474+ return;
475+ }
476+ let fx = fixture();
477+ let raw = Repository::open_bare(&fx.path).unwrap();
478+ // Advance main with a *different* file, so main and feature diverge from
479+ // their common base but do not conflict.
480+ let base = raw
481+ .find_reference("refs/heads/main")
482+ .unwrap()
483+ .target()
484+ .unwrap();
485+ commit(
486+ &raw,
487+ "main",
488+ &[base],
489+ &[("README.md", "hello\n"), ("main.txt", "m\n")],
490+ "advance main",
491+ 3,
492+ );
493+
494+ // analyze must agree it is clean...
495+ assert_eq!(
496+ analyze("git", &fx.path, fx.home.path(), "main", "feature").unwrap(),
497+ Mergeability::Clean,
498+ );
499+ // ...and each strategy must succeed, not report a phantom conflict.
500+ for (strategy, dir) in [
501+ (MergeStrategy::Merge, "wt-div-merge"),
502+ (MergeStrategy::Squash, "wt-div-squash"),
503+ (MergeStrategy::Rebase, "wt-div-rebase"),
504+ ] {
505+ let wt = fx.path.parent().unwrap().join(dir);
506+ let sha = merge(&request(&fx, strategy, &wt))
507+ .unwrap_or_else(|e| panic!("{strategy:?} failed: {e:?}"));
508+ let raw = Repository::open_bare(&fx.path).unwrap();
509+ assert!(
510+ raw.find_commit(git2::Oid::from_str(&sha).unwrap())
511+ .unwrap()
512+ .tree()
513+ .unwrap()
514+ .get_name("feature.txt")
515+ .is_some(),
516+ "{strategy:?}: merged tree keeps feature.txt"
517+ );
518+ }
519+ }
520+
521+ #[test]
460522 fn analyze_reports_clean_and_already_merged() {
461523 if !git_present() {
462524 return;
crates/web/src/pulls.rs +4 −1
@@ -617,9 +617,12 @@ async fn run_merge(
617617 .map_err(AppError::internal)?;
618618
619619 sha.map_err(|e| match e {
620- git::GitError::MergeConflict => {
620+ git::GitError::MergeConflict(detail) if detail.is_empty() => {
621621 AppError::BadRequest("The branch could not be merged cleanly.".to_string())
622622 }
623+ git::GitError::MergeConflict(detail) => {
624+ AppError::BadRequest(format!("The branch could not be merged cleanly: {detail}"))
625+ }
623626 other => AppError::from(other),
624627 })
625628 }
data/repos/01/01kyc0j4dzrnx6afv3wwfvxgn4.git/logs/HEAD +1 −0
@@ -1,2 +1,3 @@
11 0000000000000000000000000000000000000000 f09bd3e7f54bc32b967fdffb126b533e1a487f4d hanna <me@hanna.lol> 1784962339 -0400 push
22 f09bd3e7f54bc32b967fdffb126b533e1a487f4d 1570ae1be5f4b82bf24e1115681290e6d68808bf Hanna <me@hanna.lol> 1785020132 -0400
3+1570ae1be5f4b82bf24e1115681290e6d68808bf 94ffb4ef79a86c7e24d038233859149ba61439aa Hanna <me@hanna.lol> 1785020888 -0400
data/repos/01/01kyc0j4dzrnx6afv3wwfvxgn4.git/logs/refs/heads/main +1 −0
@@ -1,2 +1,3 @@
11 0000000000000000000000000000000000000000 f09bd3e7f54bc32b967fdffb126b533e1a487f4d hanna <me@hanna.lol> 1784962339 -0400 push
22 f09bd3e7f54bc32b967fdffb126b533e1a487f4d 1570ae1be5f4b82bf24e1115681290e6d68808bf Hanna <me@hanna.lol> 1785020132 -0400
3+1570ae1be5f4b82bf24e1115681290e6d68808bf 94ffb4ef79a86c7e24d038233859149ba61439aa Hanna <me@hanna.lol> 1785020888 -0400
data/repos/01/01kyc0j4dzrnx6afv3wwfvxgn4.git/objects/94/ffb4ef79a86c7e24d038233859149ba61439aa +0 −0

Binary file not shown.

data/repos/01/01kyc0j4dzrnx6afv3wwfvxgn4.git/refs/heads/main +1 −1
@@ -1 +1 @@
1-1570ae1be5f4b82bf24e1115681290e6d68808bf
1+94ffb4ef79a86c7e24d038233859149ba61439aa