LibGit2: Add wrappers for git_apply_to_tree, git_diff_from_buffer, and git_index_write_tree_to

Added Julia wrappers for three libgit2 functions with idiomatic APIs:

- `GitDiff(::AbstractString)`: Parse diffs from unified diff format buffers
- `apply_to_tree(repo, preimage, diff, options)`: Apply a diff to a tree,
  returning a GitIndex with the result
- `write_tree_to!(repo, idx)`: Write an index as a tree to a repository

Made GitDiff and GitDiffStats repository-independent since they can be
created from buffers and all operations work purely on object pointers.
Added ApplyOptions struct for apply configuration and tests for all new
functionality.

Author: Keno

stdlib/LibGit2/src/diff.jl

@@ -35,7 +35,7 @@ function diff_tree(repo::GitRepo, tree::GitTree, pathspecs::AbstractString=""; c
                      (Ptr{Ptr{Cvoid}}, Ptr{Cvoid}, Ptr{Cvoid}, Ptr{DiffOptionsStruct}),
                      diff_ptr_ptr, repo, tree, isempty(pathspecs) ? C_NULL : pathspecs)
     end
-    return GitDiff(repo, diff_ptr_ptr[])
+    return GitDiff(diff_ptr_ptr[])
 end
 
 """
@@ -54,7 +54,7 @@ function diff_tree(repo::GitRepo, oldtree::GitTree, newtree::GitTree)
     @check ccall((:git_diff_tree_to_tree, libgit2), Cint,
                   (Ptr{Ptr{Cvoid}}, Ptr{Cvoid}, Ptr{Cvoid}, Ptr{Cvoid}, Ptr{DiffOptionsStruct}),
                    diff_ptr_ptr, repo, oldtree, newtree, C_NULL)
-    return GitDiff(repo, diff_ptr_ptr[])
+    return GitDiff(diff_ptr_ptr[])
 end
 
 """
@@ -70,7 +70,7 @@ function GitDiffStats(diff::GitDiff)
     @check ccall((:git_diff_get_stats, libgit2), Cint,
                   (Ptr{Ptr{Cvoid}}, Ptr{Cvoid}),
                   diff_stat_ptr_ptr, diff)
-    return GitDiffStats(diff.owner, diff_stat_ptr_ptr[])
+    return GitDiffStats(diff_stat_ptr_ptr[])
 end
 
 """
@@ -142,3 +142,34 @@ function Base.show(io::IO, diff::GitDiff)
     println(io, "Number of deltas: $(count(diff))")
     show(io, GitDiffStats(diff))
 end
+
+"""
+    GitDiff(content::AbstractString)
+
+Parse a diff from a buffer. The `content` should be in unified diff format.
+Returns a [`GitDiff`](@ref) object.
+
+This is equivalent to [`git_diff_from_buffer`](https://libgit2.org/libgit2/#HEAD/group/diff/git_diff_from_buffer).
+
+# Examples
+```julia
+diff_str = \"\"\"
+diff --git a/file.txt b/file.txt
+index 1234567..abcdefg 100644
+--- a/file.txt
++++ b/file.txt
+@@ -1 +1 @@
+-old content
++new content
+\"\"\"
+diff = LibGit2.GitDiff(diff_str)
+```
+"""
+function GitDiff(content::AbstractString)
+    ensure_initialized()
+    diff_ptr_ptr = Ref{Ptr{Cvoid}}(C_NULL)
+    @check ccall((:git_diff_from_buffer, libgit2), Cint,
+                 (Ptr{Ptr{Cvoid}}, Cstring, Csize_t),
+                 diff_ptr_ptr, content, sizeof(content))
+    return GitDiff(diff_ptr_ptr[])
+end

stdlib/LibGit2/src/index.jl

@@ -56,6 +56,32 @@ function write_tree!(idx::GitIndex)
     return oid_ptr[]
 end
 
+"""
+    write_tree_to!(repo::GitRepo, idx::GitIndex)::GitHash
+
+Write the index `idx` as a [`GitTree`](@ref) to the given repository `repo`.
+This is similar to [`write_tree!`](@ref) but allows writing the index to a
+different repository than the one it may be associated with.
+
+Trees will be recursively created for each subtree in `idx`. The returned
+[`GitHash`](@ref) can be used to create a [`GitCommit`](@ref).
+
+This is equivalent to [`git_index_write_tree_to`](https://libgit2.org/libgit2/#HEAD/group/index/git_index_write_tree_to).
+
+# Examples
+```julia
+idx = LibGit2.GitIndex(source_repo)
+tree_oid = LibGit2.write_tree_to!(target_repo, idx)
+```
+"""
+function write_tree_to!(repo::GitRepo, idx::GitIndex)
+    ensure_initialized()
+    oid_ptr = Ref(GitHash())
+    @check ccall((:git_index_write_tree_to, libgit2), Cint,
+                 (Ptr{GitHash}, Ptr{Cvoid}, Ptr{Cvoid}), oid_ptr, idx, repo)
+    return oid_ptr[]
+end
+
 function repository(idx::GitIndex)
     if idx.owner === nothing
         throw(GitError(Error.Index, Error.ENOTFOUND, "Index does not have an owning repository."))

stdlib/LibGit2/src/tree.jl

@@ -194,3 +194,35 @@ end
 function Base.haskey(tree::GitTree, target::AbstractString)
     return _getindex(tree, target) !== nothing
 end
+
+"""
+    apply_to_tree(repo::GitRepo, preimage::GitTree, diff::GitDiff, options::ApplyOptions=ApplyOptions())
+
+Apply a [`GitDiff`](@ref) to a [`GitTree`](@ref), returning the resulting index.
+The `preimage` is the tree to which the diff will be applied. The `diff` should be
+generated from the `preimage` to some other tree.
+
+The returned [`GitIndex`](@ref) contains the result of applying the diff and can be
+written as a tree using [`write_tree_to!`](@ref).
+
+This is equivalent to [`git_apply_to_tree`](https://libgit2.org/libgit2/#HEAD/group/apply/git_apply_to_tree).
+
+# Examples
+```julia
+repo = LibGit2.GitRepo(repo_path)
+tree1 = LibGit2.GitTree(repo, "HEAD^{tree}")
+tree2 = LibGit2.GitTree(repo, "HEAD~1^{tree}")
+diff = LibGit2.diff_tree(repo, tree1, tree2)
+result_index = LibGit2.apply_to_tree(repo, tree1, diff)
+tree_oid = LibGit2.write_tree_to!(repo, result_index)
+```
+"""
+function apply_to_tree(repo::GitRepo, preimage::GitTree, diff::GitDiff, options::ApplyOptions=ApplyOptions())
+    ensure_initialized()
+    out_index_ptr = Ref{Ptr{Cvoid}}(C_NULL)
+    opts_ptr = Ref(options)
+    @check ccall((:git_apply_to_tree, libgit2), Cint,
+                 (Ptr{Ptr{Cvoid}}, Ptr{Cvoid}, Ptr{Cvoid}, Ptr{Cvoid}, Ptr{ApplyOptions}),
+                 out_index_ptr, repo, preimage, diff, opts_ptr)
+    return GitIndex(nothing, out_index_ptr[])
+end

stdlib/LibGit2/src/types.jl

@@ -859,6 +859,28 @@ The fields represent:
 end
 @assert Base.allocatedinline(StatusOptions)
 
+"""
+    LibGit2.ApplyOptions
+
+Options for applying a diff.
+Matches the [`git_apply_options`](https://libgit2.org/libgit2/#HEAD/type/git_apply_options) struct.
+
+The fields represent:
+  * `version`: version of the struct in use, in case this changes later. For now, always `1`.
+  * `delta_cb`: optional callback that will be made before each delta is applied.
+  * `hunk_cb`: optional callback that will be made before each hunk is applied.
+  * `payload`: the payload for the callback functions.
+  * `flags`: flags controlling how the apply is performed (e.g., check mode).
+"""
+@kwdef struct ApplyOptions
+    version::Cuint           = Cuint(1)
+    delta_cb::Ptr{Cvoid}     = C_NULL
+    hunk_cb::Ptr{Cvoid}      = C_NULL
+    payload::Any             = nothing
+    flags::Cuint             = Cuint(0)
+end
+@assert Base.allocatedinline(ApplyOptions)
+
 """
     LibGit2.StatusEntry
 
@@ -1042,8 +1064,8 @@ for (typ, owntyp, sup, cname) in Tuple{Symbol,Any,Symbol,Symbol}[
     (:GitRevWalker,      :GitRepo,                :AbstractGitObject, :git_revwalk),
     (:GitReference,      :GitRepo,                :AbstractGitObject, :git_reference),
     (:GitDescribeResult, :GitRepo,                :AbstractGitObject, :git_describe_result),
-    (:GitDiff,           :GitRepo,                :AbstractGitObject, :git_diff),
-    (:GitDiffStats,      :GitRepo,                :AbstractGitObject, :git_diff_stats),
+    (:GitDiff,           nothing,                 :AbstractGitObject, :git_diff),
+    (:GitDiffStats,      nothing,                 :AbstractGitObject, :git_diff_stats),
     (:GitAnnotated,      :GitRepo,                :AbstractGitObject, :git_annotated_commit),
     (:GitRebase,         :GitRepo,                :AbstractGitObject, :git_rebase),
     (:GitBlame,          :GitRepo,                :AbstractGitObject, :git_blame),

stdlib/LibGit2/test/libgit2-tests.jl

@@ -1147,6 +1147,20 @@ mktempdir() do dir
                 @test !LibGit2.isdirty(repo, cached=true)
                 @test !LibGit2.isdiff(repo, "HEAD", cached=true)
             end
+
+            LibGit2.with(LibGit2.GitRepo(cache_repo)) do repo
+                diff_str = "diff --git a/test.txt b/test.txt\nindex 0000000..1111111 100644\n"
+                @test_throws LibGit2.GitError LibGit2.GitDiff(diff_str)
+
+                tree1 = LibGit2.GitTree(repo, "HEAD~1^{tree}")
+                tree2 = LibGit2.GitTree(repo, "HEAD^{tree}")
+                diff = LibGit2.diff_tree(repo, tree1, tree2)
+                idx = LibGit2.apply_to_tree(repo, tree1, diff)
+                @test idx isa LibGit2.GitIndex
+                oid = LibGit2.write_tree_to!(repo, idx)
+                @test oid isa LibGit2.GitHash
+                close(idx)
+            end
         end
     end