feat(backend) update (unfinished)

backend/server/src/utils/git.rs

@@ -0,0 +1,195 @@
+/// git merge
+/// based on https://github.com/rust-lang/git2-rs/blob/master/examples/pull.rs
+/// https://github.com/rust-lang/git2-rs/commit/f3b87baed1e33d6c2d94fe1fa6aa6503a071d837
+///
+use git2::{
+    build, AnnotatedCommit, AutotagOption, Delta, FetchOptions, Reference, Remote, Repository,
+};
+use std::path::PathBuf;
+use tracing::{error, warn};
+
+
+#[derive(Debug, Eq, PartialEq)]
+pub struct FileDelta {
+    pub old_path: Option<PathBuf>,
+    pub new_path: Option<PathBuf>,
+    pub status: Delta,
+}
+
+fn do_fetch<'a>(
+    repo: &'a Repository,
+    refs: &[&str],
+    remote: &'a mut Remote,
+) -> Result<AnnotatedCommit<'a>, git2::Error> {
+    let mut fetch_option = FetchOptions::new();
+
+    // Always fetch all tags.
+    // Perform a download and also update tips
+    fetch_option.download_tags(AutotagOption::All);
+    remote.fetch(refs, Some(&mut fetch_option), None)?;
+
+    let fetch_head = repo.find_reference("FETCH_HEAD")?;
+    repo.reference_to_annotated_commit(&fetch_head)
+}
+
+fn fast_forward(
+    repo: &Repository,
+    lb: &mut Reference,
+    rc: &AnnotatedCommit,
+) -> Result<(), git2::Error> {
+    let name = match lb.name() {
+        Some(s) => s.to_string(),
+        None => String::from_utf8_lossy(lb.name_bytes()).to_string(),
+    };
+    let msg = format!("fast-forward({}) -> {}", name, rc.id());
+    // println!("{}", msg);
+    lb.set_target(rc.id(), &msg)?;
+    repo.set_head(&name)?;
+    repo.checkout_head(Some(
+        build::CheckoutBuilder::default()
+            // For some reason, the force is required to make the working directory actually get updated
+            // I suspect we should be adding some logic to handle dirty working directory states,
+            // but this is just an example so maybe not.
+            .force(),
+    ))?;
+    Ok(())
+}
+
+fn normal_merge(
+    repo: &Repository,
+    local: &AnnotatedCommit,
+    remote: &AnnotatedCommit,
+) -> Result<(), git2::Error> {
+    let local_tree = repo.find_commit(local.id())?.tree()?;
+    let remote_tree = repo.find_commit(remote.id())?.tree()?;
+    let ancestor = repo
+        .find_commit(repo.merge_base(local.id(), remote.id())?)?
+        .tree()?;
+    let mut idx = repo.merge_trees(&ancestor, &local_tree, &remote_tree, None)?;
+
+    if idx.has_conflicts() {
+        warn!("merge conflicts detected");
+        repo.checkout_index(Some(&mut idx), None)?;
+        return Ok(());
+    }
+    let result_tree = repo.find_tree(idx.write_tree_to(repo)?)?;
+    // now create the merge commit
+    let msg = format!("merge({}) -> {}", remote.id(), local.id());
+    let sig = repo.signature()?;
+    let local_commit = repo.find_commit(local.id())?;
+    let remote_commit = repo.find_commit(remote.id())?;
+
+    // Do our merge commit and set the current branch head to that commit.
+    let _merge_commit = repo.commit(
+        Some("HEAD"),
+        &sig,
+        &sig,
+        &msg,
+        &result_tree,
+        &[&local_commit, &remote_commit],
+    )?;
+    // Set working tree to match head.
+    repo.checkout_head(None)?;
+    Ok(())
+}
+
+fn do_merge<'a>(
+    repo: &'a Repository,
+    remote_branch: &str,
+    fetch_commit: AnnotatedCommit<'a>,
+) -> Result<Vec<FileDelta>, git2::Error> {
+    // 1. do a merge analysis
+    let analysis = repo.merge_analysis(&[&fetch_commit])?;
+
+    let head_commit = repo.reference_to_annotated_commit(&repo.head()?)?;
+
+    // 2. Do the appropriate merge
+    if analysis.0.is_fast_forward() {
+        // println!("Doing a fast-forward");
+        // do a fast-forward
+        let ref_name = format!("refs/heads/{}", remote_branch);
+        match repo.find_reference(&ref_name) {
+            Ok(mut r) => {
+                fast_forward(repo, &mut r, &fetch_commit)?;
+            }
+            Err(_) => {
+                // The branch doesn't exist, so set the reference to the
+                // commit directly. Usually this is because you are pulling
+                // into an empty repository.
+                repo.reference(
+                    &ref_name,
+                    fetch_commit.id(),
+                    true,
+                    &format!("({}) -> {}", remote_branch, fetch_commit.id()),
+                )?;
+                repo.set_head(&ref_name)?;
+                repo.checkout_head(Some(
+                    build::CheckoutBuilder::default()
+                        .allow_conflicts(true)
+                        .conflict_style_merge(true)
+                        .force(),
+                ))?;
+            }
+        };
+    } else if analysis.0.is_normal() {
+        // do a normal merge
+        normal_merge(repo, &head_commit, &fetch_commit)?;
+    }
+    // else {
+    //     // already up-to-date
+    //     println!("Nothing to do...");
+    // }
+
+    calculate_diff(repo, &head_commit, &fetch_commit)
+}
+
+fn calculate_diff(
+    repo: &Repository,
+    local: &AnnotatedCommit,
+    remote: &AnnotatedCommit,
+) -> Result<Vec<FileDelta>, git2::Error> {
+    let local_tree = repo.find_commit(local.id())?.tree()?;
+    let remote_tree = repo.find_commit(remote.id())?.tree()?;
+    let diff = repo.diff_tree_to_tree(Some(&local_tree), Some(&remote_tree), None)?;
+
+    let mut updated_files: Vec<FileDelta> = Vec::new();
+
+    if let Err(e) = diff.foreach(
+        &mut |d, _| {
+            // let delta = d.status();
+            //
+            // let n_path = d.new_file().path();
+            // let o_path = d.old_file().path();
+            //
+            // if let Some(path) = n_path {
+            //     updated_files.insert(path.to_owned());
+            // }
+            // if let Some(path) = o_path {
+            //     updated_files.insert(path.to_owned());
+            // }
+            updated_files.push(FileDelta {
+                old_path: d.old_file().path().map(PathBuf::from),
+                new_path: d.new_file().path().map(PathBuf::from),
+                status: d.status(),
+            });
+            true // Continue
+        },
+        None,
+        None,
+        None,
+    ) {
+        error!("error at calculating diff: {:?}", e);
+    }
+
+    Ok(updated_files.into_iter().collect())
+}
+
+pub fn sync(
+    remote_name: &str,
+    remote_branch: &str,
+    repo: &Repository,
+) -> Result<Vec<FileDelta>, git2::Error> {
+    let mut remote = repo.find_remote(remote_name)?;
+    let fetch_commit = do_fetch(repo, &[remote_branch], &mut remote)?;
+    do_merge(repo, remote_branch, fetch_commit)
+}