feat: add Repository::merge_trees()

Author: Byron

gix/Cargo.toml

@@ -139,7 +139,7 @@ revparse-regex = ["regex", "revision"]
 blob-diff = ["gix-diff/blob", "attributes"]
 
 ## Add functions to specifically merge files, using the standard three-way merge that git offers.
-blob-merge = ["dep:gix-merge", "attributes"]
+blob-merge = ["blob-diff", "dep:gix-merge", "attributes"]
 
 ## Make it possible to turn a tree into a stream of bytes, which can be decoded to entries and turned into various other formats.
 worktree-stream = ["gix-worktree-stream", "attributes"]

gix/src/config/tree/sections/merge.rs

@@ -1,7 +1,7 @@
 use crate::config;
 use crate::config::tree::SubSectionRequirement;
 use crate::config::{
-    tree::{diff, keys, Key, Merge, Section},
+    tree::{keys, Key, Merge, Section},
     Tree,
 };
 
@@ -15,7 +15,8 @@ impl Merge {
         "The limit is actually squared, so 1000 stands for up to 1 million diffs if fuzzy rename tracking is enabled",
     );
     /// The `merge.renames` key.
-    pub const RENAMES: diff::Renames = diff::Renames::new_renames("renames", &config::Tree::MERGE);
+    #[cfg(feature = "blob-merge")]
+    pub const RENAMES: super::diff::Renames = super::diff::Renames::new_renames("renames", &config::Tree::MERGE);
     /// The `merge.renormalize` key
     pub const RENORMALIZE: keys::Boolean = keys::Boolean::new_boolean("renormalize", &Tree::MERGE);
     /// The `merge.default` key
@@ -43,6 +44,7 @@ impl Section for Merge {
     fn keys(&self) -> &[&dyn Key] {
         &[
             &Self::RENAME_LIMIT,
+            #[cfg(feature = "blob-merge")]
             &Self::RENAMES,
             &Self::RENORMALIZE,
             &Self::DEFAULT,

gix/src/diff.rs

@@ -122,7 +122,7 @@ pub mod rename {
 
 ///
 #[cfg(feature = "blob-diff")]
-mod utils {
+pub(crate) mod utils {
     use gix_diff::{rewrites::Copies, Rewrites};
 
     use crate::{
@@ -172,10 +172,18 @@ mod utils {
         config: &gix_config::File<'static>,
         lenient: bool,
     ) -> Result<Option<Rewrites>, new_rewrites::Error> {
-        let key = "diff.renames";
+        new_rewrites_inner(config, lenient, &Diff::RENAMES, &Diff::RENAME_LIMIT)
+    }
+
+    pub fn new_rewrites_inner(
+        config: &gix_config::File<'static>,
+        lenient: bool,
+        renames: &'static crate::config::tree::diff::Renames,
+        rename_limit: &'static crate::config::tree::keys::UnsignedInteger,
+    ) -> Result<Option<Rewrites>, new_rewrites::Error> {
         let copies = match config
-            .boolean(key)
-            .map(|value| Diff::RENAMES.try_into_renames(value))
+            .boolean(renames)
+            .map(|value| renames.try_into_renames(value))
             .transpose()
             .with_leniency(lenient)?
         {
@@ -191,8 +199,8 @@ mod utils {
         Ok(Rewrites {
             copies,
             limit: config
-                .integer("diff.renameLimit")
-                .map(|value| Diff::RENAME_LIMIT.try_into_usize(value))
+                .integer(rename_limit)
+                .map(|value| rename_limit.try_into_usize(value))
                 .transpose()
                 .with_leniency(lenient)?
                 .unwrap_or(default.limit),

gix/src/repository/merge.rs

@@ -1,16 +1,17 @@
 use crate::config::cache::util::ApplyLeniencyDefault;
 use crate::config::tree;
-use crate::repository::{blob_merge_options, merge_resource_cache};
+use crate::repository::{blob_merge_options, merge_resource_cache, merge_trees, tree_merge_options};
 use crate::Repository;
 use gix_merge::blob::builtin_driver::text;
+use gix_object::Write;
 use std::borrow::Cow;
 
 /// Merge-utilities
 impl Repository {
     /// Create a resource cache that can hold the three resources needed for a three-way merge. `worktree_roots`
     /// determines which side of the merge is read from the worktree, or from which worktree.
     ///
-    /// The platform can be used to setup resources and finally perform a merge.
+    /// The platform can be used to set up resources and finally perform a merge among blobs.
     ///
     /// Note that the current index is used for attribute queries.
     pub fn merge_resource_cache(
@@ -55,7 +56,8 @@ impl Repository {
         Ok(gix_merge::blob::Platform::new(filter, mode, attrs, drivers, options))
     }
 
-    /// Return options for use with [`gix_merge::blob::PlatformRef::merge()`].
+    /// Return options for use with [`gix_merge::blob::PlatformRef::merge()`], accessible through
+    /// [merge_resource_cache()](Self::merge_resource_cache).
     pub fn blob_merge_options(&self) -> Result<gix_merge::blob::platform::merge::Options, blob_merge_options::Error> {
         Ok(gix_merge::blob::platform::merge::Options {
             is_virtual_ancestor: false,
@@ -79,4 +81,58 @@ impl Repository {
             },
         })
     }
+
+    /// Read all relevant configuration options to instantiate options for use in [`merge_trees()`](Self::merge_trees).
+    pub fn tree_merge_options(&self) -> Result<gix_merge::tree::Options, tree_merge_options::Error> {
+        Ok(gix_merge::tree::Options {
+            rewrites: crate::diff::utils::new_rewrites_inner(
+                &self.config.resolved,
+                self.config.lenient_config,
+                &tree::Merge::RENAMES,
+                &tree::Merge::RENAME_LIMIT,
+            )?,
+            blob_merge: self.blob_merge_options()?,
+            blob_merge_command_ctx: self.command_context()?,
+            fail_on_conflict: None,
+            marker_size_multiplier: 0,
+            symlink_conflicts: None,
+            allow_lossy_resolution: false,
+        })
+    }
+
+    /// Merge `our_tree` and `their_tree` together, assuming they have the same `ancestor_tree`, to yield a new tree
+    /// which is provided as [tree editor](gix_object::tree::Editor) to inspect and finalize results at will.
+    /// No change to the worktree or index is made, but objects may be written to the object database as merge results
+    /// are stored.
+    /// If these changes should not be observable outside of this instance, consider [enabling object memory](Self::with_object_memory).
+    ///
+    /// Note that `ancestor_tree` can be the [empty tree hash](gix_hash::ObjectId::empty_tree) to indicate no common ancestry.
+    ///
+    /// `labels` are typically chosen to identify the refs or names for `our_tree` and `their_tree` and `ancestor_tree` respectively.
+    ///
+    /// `options` should be initialized with [`tree_merge_options()`](Self::tree_merge_options()).
+    // TODO: Use `crate::merge::Options` here and add niceties such as setting the resolution strategy.
+    pub fn merge_trees(
+        &self,
+        ancestor_tree: impl AsRef<gix_hash::oid>,
+        our_tree: impl AsRef<gix_hash::oid>,
+        their_tree: impl AsRef<gix_hash::oid>,
+        labels: gix_merge::blob::builtin_driver::text::Labels<'_>,
+        options: gix_merge::tree::Options,
+    ) -> Result<gix_merge::tree::Outcome<'_>, merge_trees::Error> {
+        let mut diff_cache = self.diff_resource_cache_for_tree_diff()?;
+        let mut blob_merge = self.merge_resource_cache(Default::default())?;
+        Ok(gix_merge::tree(
+            ancestor_tree.as_ref(),
+            our_tree.as_ref(),
+            their_tree.as_ref(),
+            labels,
+            &self.objects,
+            |buf| self.objects.write_buf(gix_object::Kind::Blob, buf),
+            &mut Default::default(),
+            &mut diff_cache,
+            &mut blob_merge,
+            options,
+        )?)
+    }
 }

gix/src/repository/mod.rs

@@ -112,6 +112,38 @@ pub mod merge_resource_cache {
     }
 }
 
+///
+#[cfg(feature = "blob-merge")]
+pub mod merge_trees {
+    /// The error returned by [Repository::merge_trees()](crate::Repository::merge_trees()).
+    #[derive(Debug, thiserror::Error)]
+    #[allow(missing_docs)]
+    pub enum Error {
+        #[error(transparent)]
+        MergeResourceCache(#[from] super::merge_resource_cache::Error),
+        #[error(transparent)]
+        DiffResourceCache(#[from] super::diff_resource_cache::Error),
+        #[error(transparent)]
+        TreeMerge(#[from] gix_merge::tree::Error),
+    }
+}
+
+///
+#[cfg(feature = "blob-merge")]
+pub mod tree_merge_options {
+    /// The error returned by [Repository::tree_merge_options()](crate::Repository::tree_merge_options()).
+    #[derive(Debug, thiserror::Error)]
+    #[allow(missing_docs)]
+    pub enum Error {
+        #[error(transparent)]
+        BlobMergeOptions(#[from] super::blob_merge_options::Error),
+        #[error(transparent)]
+        RewritesConfig(#[from] crate::diff::new_rewrites::Error),
+        #[error(transparent)]
+        CommandContext(#[from] crate::config::command_context::Error),
+    }
+}
+
 ///
 #[cfg(feature = "blob-diff")]
 pub mod diff_resource_cache {