rebase: introduce inmemory rebasing

Introduce the ability to rebase in-memory or in a bare repository.

When `rebase_options.inmemory` is specified, the resultant `git_rebase`
session will not be persisted to disk.  Callers may still analyze
the rebase operations, resolve any conflicts against the in-memory
index and create the commits.  Neither `HEAD` nor the working
directory will be updated during this process.

include/git2/rebase.h

@@ -39,6 +39,15 @@ typedef struct {
 	int quiet;
 
 	/**
+	 * Used by `git_rebase_init`, this will begin an in-memory rebase,
+	 * which will allow callers to step through the rebase operations and
+	 * commit the rebased changes, but will not rewind HEAD or update the
+	 * repository to be in a rebasing state.  This will not interfere with
+	 * the working directory (if there is one).
+	 */
+	int inmemory;
+
+	/**
 	 * Used by `git_rebase_finish`, this is the name of the notes reference
 	 * used to rewrite notes for rebased commits when finishing the rebase;
 	 * if NULL, the contents of the configuration option `notes.rewriteRef`
@@ -101,7 +110,7 @@ typedef enum {
 
 #define GIT_REBASE_OPTIONS_VERSION 1
 #define GIT_REBASE_OPTIONS_INIT \
-	{GIT_REBASE_OPTIONS_VERSION, 0, NULL, GIT_CHECKOUT_OPTIONS_INIT}
+	{GIT_REBASE_OPTIONS_VERSION, 0, 0, NULL, GIT_CHECKOUT_OPTIONS_INIT}
 
 /** Indicates that a rebase operation is not (yet) in progress. */
 #define GIT_REBASE_NO_OPERATION SIZE_MAX
@@ -127,6 +136,12 @@ typedef struct {
 	 * be populated for operations of type `GIT_REBASE_OPERATION_EXEC`.
 	 */
 	const char *exec;
+
+	/**
+	 * The index that is the result of an operation.
+	 * This is set only for in-memory rebases.
+	 */
+	git_index *index;
 } git_rebase_operation;
 
 /**

tests/rebase/inmemory.c

+#include "clar_libgit2.h"
+#include "git2/rebase.h"
+#include "posix.h"
+
+#include <fcntl.h>
+
+static git_repository *repo;
+
+// Fixture setup and teardown
+void test_rebase_inmemory__initialize(void)
+{
+	repo = cl_git_sandbox_init("rebase");
+}
+
+void test_rebase_inmemory__cleanup(void)
+{
+	cl_git_sandbox_cleanup();
+}
+
+void test_rebase_inmemory__not_in_rebase_state(void)
+{
+	git_rebase *rebase;
+	git_reference *branch_ref, *upstream_ref;
+	git_annotated_commit *branch_head, *upstream_head;
+	git_rebase_options opts = GIT_REBASE_OPTIONS_INIT;
+
+	opts.inmemory = true;
+
+	cl_git_pass(git_reference_lookup(&branch_ref, repo, "refs/heads/beef"));
+	cl_git_pass(git_reference_lookup(&upstream_ref, repo, "refs/heads/master"));
+
+	cl_git_pass(git_annotated_commit_from_ref(&branch_head, repo, branch_ref));
+	cl_git_pass(git_annotated_commit_from_ref(&upstream_head, repo, upstream_ref));
+
+	cl_git_pass(git_rebase_init(&rebase, repo, branch_head, upstream_head, NULL, &opts));
+
+	cl_assert_equal_i(GIT_REPOSITORY_STATE_NONE, git_repository_state(repo));
+
+	git_rebase_free(rebase);
+
+	git_annotated_commit_free(branch_head);
+	git_annotated_commit_free(upstream_head);
+
+	git_reference_free(branch_ref);
+	git_reference_free(upstream_ref);
+}
+
+void test_rebase_inmemory__can_resolve_conflicts(void)
+{
+	git_rebase *rebase;
+	git_reference *branch_ref, *upstream_ref;
+	git_annotated_commit *branch_head, *upstream_head;
+	git_rebase_operation *rebase_operation;
+	git_status_list *status_list;
+	git_oid pick_id, commit_id, expected_commit_id;
+	git_signature *signature;
+	git_index *repo_index;
+	git_index_entry resolution = {{0}};
+	git_rebase_options opts = GIT_REBASE_OPTIONS_INIT;
+
+	cl_git_pass(git_signature_new(&signature,
+		"Rebaser", "rebaser@rebaser.rb", 1405694510, 0));
+
+	opts.inmemory = true;
+
+	cl_git_pass(git_reference_lookup(&branch_ref, repo, "refs/heads/asparagus"));
+	cl_git_pass(git_reference_lookup(&upstream_ref, repo, "refs/heads/master"));
+
+	cl_git_pass(git_annotated_commit_from_ref(&branch_head, repo, branch_ref));
+	cl_git_pass(git_annotated_commit_from_ref(&upstream_head, repo, upstream_ref));
+
+	cl_git_pass(git_rebase_init(&rebase, repo, branch_head, upstream_head, NULL, &opts));
+
+	cl_git_pass(git_rebase_next(&rebase_operation, rebase));
+
+	git_oid_fromstr(&pick_id, "33f915f9e4dbd9f4b24430e48731a59b45b15500");
+
+	cl_assert_equal_i(GIT_REBASE_OPERATION_PICK, rebase_operation->type);
+	cl_assert_equal_oid(&pick_id, &rebase_operation->id);
+
+	/* ensure that we did not do anything stupid to the workdir or repo index */
+	cl_git_pass(git_repository_index(&repo_index, repo));
+	cl_assert(!git_index_has_conflicts(repo_index));
+
+	cl_git_pass(git_status_list_new(&status_list, repo, NULL));
+	cl_assert_equal_i(0, git_status_list_entrycount(status_list));
+
+	/* but that the index returned from rebase does have conflicts */
+	cl_assert(git_index_has_conflicts(rebase_operation->index));
+
+	cl_git_fail_with(GIT_EUNMERGED, git_rebase_commit(&commit_id, rebase, NULL, signature, NULL, NULL));
+
+	/* ensure that we can work with the in-memory index to resolve the conflict */
+	resolution.path = "asparagus.txt";
+	resolution.mode = GIT_FILEMODE_BLOB;
+	git_oid_fromstr(&resolution.id, "414dfc71ead79c07acd4ea47fecf91f289afc4b9");
+	cl_git_pass(git_index_conflict_remove(rebase_operation->index, "asparagus.txt"));
+	cl_git_pass(git_index_add(rebase_operation->index, &resolution));
+
+	/* and finally create a commit for the resolved rebase operation */
+	cl_git_pass(git_rebase_commit(&commit_id, rebase, NULL, signature, NULL, NULL));
+
+	cl_git_pass(git_oid_fromstr(&expected_commit_id, "db7af47222181e548810da2ab5fec0e9357c5637"));
+	cl_assert_equal_oid(&commit_id, &expected_commit_id);
+
+	git_signature_free(signature);
+	git_status_list_free(status_list);
+	git_annotated_commit_free(branch_head);
+	git_annotated_commit_free(upstream_head);
+	git_reference_free(branch_ref);
+	git_reference_free(upstream_ref);
+	git_index_free(repo_index);
+	git_rebase_free(rebase);
+}

tests/rebase/iterator.c

@@ -46,26 +46,32 @@ static void test_operations(git_rebase *rebase, size_t expected_current)
 	}
 }
 
-void test_rebase_iterator__iterates(void)
+void test_iterator(bool inmemory)
 {
 	git_rebase *rebase;
+	git_rebase_options opts = GIT_REBASE_OPTIONS_INIT;
 	git_reference *branch_ref, *upstream_ref;
 	git_annotated_commit *branch_head, *upstream_head;
 	git_rebase_operation *rebase_operation;
 	git_oid commit_id;
 	int error;
 
+	opts.inmemory = inmemory;
+
 	cl_git_pass(git_reference_lookup(&branch_ref, repo, "refs/heads/beef"));
 	cl_git_pass(git_reference_lookup(&upstream_ref, repo, "refs/heads/master"));
 
 	cl_git_pass(git_annotated_commit_from_ref(&branch_head, repo, branch_ref));
 	cl_git_pass(git_annotated_commit_from_ref(&upstream_head, repo, upstream_ref));
 
-	cl_git_pass(git_rebase_init(&rebase, repo, branch_head, upstream_head, NULL, NULL));
+	cl_git_pass(git_rebase_init(&rebase, repo, branch_head, upstream_head, NULL, &opts));
 	test_operations(rebase, GIT_REBASE_NO_OPERATION);
-	git_rebase_free(rebase);
 
-	cl_git_pass(git_rebase_open(&rebase, repo, NULL));
+	if (!inmemory) {
+		git_rebase_free(rebase);
+		cl_git_pass(git_rebase_open(&rebase, repo, NULL));
+	}
+
 	cl_git_pass(git_rebase_next(&rebase_operation, rebase));
 	cl_git_pass(git_rebase_commit(&commit_id, rebase, NULL, signature,
 		NULL, NULL));
@@ -81,8 +87,10 @@ void test_rebase_iterator__iterates(void)
 		NULL, NULL));
 	test_operations(rebase, 2);
 
-	git_rebase_free(rebase);
-	cl_git_pass(git_rebase_open(&rebase, repo, NULL));
+	if (!inmemory) {
+		git_rebase_free(rebase);
+		cl_git_pass(git_rebase_open(&rebase, repo, NULL));
+	}
 
 	cl_git_pass(git_rebase_next(&rebase_operation, rebase));
 	cl_git_pass(git_rebase_commit(&commit_id, rebase, NULL, signature,
@@ -104,3 +112,13 @@ void test_rebase_iterator__iterates(void)
 	git_reference_free(upstream_ref);
 	git_rebase_free(rebase);
 }
+
+void test_rebase_iterator__iterates(void)
+{
+	test_iterator(false);
+}
+
+void test_rebase_iterator__iterates_inmemory(void)
+{
+	test_iterator(true);
+}