Increase error tolerance

src/git.rs

@@ -14,7 +14,7 @@ mod rev_list;
 mod switch;
 
 pub use branch::{branch, StartingPoint};
-pub use cherry_pick::cherry_pick;
+pub use cherry_pick::{cherry_pick, cherry_pick_abort};
 pub use commit::commit;
 pub use fetch::fetch;
 pub use log::log;

src/git/cherry_pick.rs

@@ -18,3 +18,16 @@ impl GitCmd for CherryPick {
         cmd.arg("cherry-pick").arg(self.commit);
     }
 }
+
+#[derive(Default)]
+pub struct CherryPickAbort;
+
+pub fn cherry_pick_abort() -> CherryPickAbort {
+    CherryPickAbort
+}
+
+impl GitCmd for CherryPickAbort {
+    fn setup(self, cmd: &mut Command) {
+        cmd.arg("cherry-pick").arg("--abort");
+    }
+}

src/upstream.rs

@@ -141,6 +141,57 @@ pub fn maybe_prefix_cherry_picked_commit() -> Result<(), Error> {
     Ok(())
 }
 
+// returns (them_msg, us)
+fn find_last_upstreamed_commit_us() -> Result<(String, String), Error> {
+    let mut branch = git::Branch("gcc/trunk".to_owned());
+
+    loop {
+        let last_upstreamed_commit = git::log()
+            .amount(1)
+            .grep("gccrs: ")
+            .branch(branch)
+            .format(git::Format::Hash)
+            .spawn()?
+            .stdout
+            .trim_end()
+            .to_owned();
+
+        info!("found last upstreamed commit: {}", last_upstreamed_commit);
+
+        let last_msg = git::log()
+            .amount(1)
+            .branch(git::Branch(last_upstreamed_commit.as_str()))
+            .format(git::Format::Title)
+            .spawn()?
+            .stdout
+            .strip_prefix("gccrs: ")
+            .unwrap()
+            .trim_end()
+            .to_owned();
+
+        info!("commit title: {}", last_msg);
+
+        let last_commit_us = git::log()
+            .amount(1)
+            .grep(last_msg.as_str())
+            .branch(git::Branch("upstream/master"))
+            .grep(last_msg.as_str())
+            .format(git::Format::Hash)
+            .spawn()?
+            .stdout
+            .trim_end()
+            .to_owned();
+
+        if last_commit_us.is_empty() {
+            info!("could not find matching commit, skipping");
+            branch = git::Branch(last_upstreamed_commit + "~");
+        } else {
+            info!("found equivalent commit: {}", last_commit_us);
+            return Ok((last_msg, last_commit_us));
+        }
+    }
+}
+
 fn prepare_body(last_commit: String, rev_list: String) -> String {
     format!(
         "
@@ -176,31 +227,8 @@ pub async fn prepare_commits(
     info!("fetching `gcc`...");
     git::fetch().remote("gcc").spawn()?;
 
-    let last_upstreamed_commit = git::log()
-        .amount(1)
-        .grep("gccrs: ")
-        .branch(git::Branch("gcc/trunk"))
-        .format(git::Format::Title)
-        .spawn()?
-        .stdout;
-
-    info!("found last upstreamed commit: {}", last_upstreamed_commit);
-
-    let last_msg = last_upstreamed_commit
-        .strip_prefix("gccrs: ")
-        .unwrap()
-        .trim_end();
-
-    let last_commit_us = git::log()
-        .amount(1)
-        .grep(last_msg)
-        .branch(git::Branch("upstream/master"))
-        .grep(last_msg)
-        .format(git::Format::Hash)
-        .spawn()?
-        .stdout;
-
-    info!("found equivalent commit: {}", last_commit_us);
+    let (last_upstreamed_commit, last_commit_us)
+      = find_last_upstreamed_commit_us()?;
 
     let rev_list = git::rev_list(last_commit_us, "upstream/master")
         .no_merges()
@@ -224,12 +252,30 @@ pub async fn prepare_commits(
 
     info!("created branch `{new_branch}`");
 
-    rev_list.lines().try_for_each(|commit| {
+    // cherry-pick until we hit a commit we can't apply
+    // if we hit such a commit, only error if we haven't applied any commits
+    let mut had_successful_cherry_pick = false;
+    for commit in rev_list.lines() {
         info!("cherry-picking {commit}...");
-        git::cherry_pick(git::Commit(commit)).spawn()?;
 
-        maybe_prefix_cherry_picked_commit()
-    })?;
+        match git::cherry_pick(git::Commit(commit)).spawn() {
+            Err(e_cherry) => {
+                if !had_successful_cherry_pick {
+                    info!("failed on first commit");
+                    return Err(Error::Git(e_cherry))
+                } else if let Err(e_abort) = git::cherry_pick_abort().spawn() {
+                    info!("failed to abort cherry-pick");
+                    return Err(Error::Git(e_abort))
+                } else {
+                    info!("failed, stopping early");
+                    break
+                }
+            }
+            _ => had_successful_cherry_pick = true
+        }
+
+        maybe_prefix_cherry_picked_commit()?;
+    }
 
     info!("pushing branch...");
     git::push()