Merge branch 'en/merge-ort-api-null-impl'

Preparation for a new merge strategy.

* en/merge-ort-api-null-impl:
  merge,rebase,revert: select ort or recursive by config or environment
  fast-rebase: demonstrate merge-ort's API via new test-tool command
  merge-ort-wrappers: new convience wrappers to mimic the old merge API
  merge-ort: barebones API of new merge strategy with empty implementation

Author: gitster

Makefile

@@ -705,6 +705,7 @@ TEST_BUILTINS_OBJS += test-dump-fsmonitor.o
 TEST_BUILTINS_OBJS += test-dump-split-index.o
 TEST_BUILTINS_OBJS += test-dump-untracked-cache.o
 TEST_BUILTINS_OBJS += test-example-decorate.o
+TEST_BUILTINS_OBJS += test-fast-rebase.o
 TEST_BUILTINS_OBJS += test-genrandom.o
 TEST_BUILTINS_OBJS += test-genzeros.o
 TEST_BUILTINS_OBJS += test-hash-speed.o
@@ -922,6 +923,8 @@ LIB_OBJS += mailmap.o
 LIB_OBJS += match-trees.o
 LIB_OBJS += mem-pool.o
 LIB_OBJS += merge-blobs.o
+LIB_OBJS += merge-ort.o
+LIB_OBJS += merge-ort-wrappers.o
 LIB_OBJS += merge-recursive.o
 LIB_OBJS += merge.o
 LIB_OBJS += mergesort.o

builtin/merge.c

@@ -28,6 +28,7 @@
 #include "rerere.h"
 #include "help.h"
 #include "merge-recursive.h"
+#include "merge-ort-wrappers.h"
 #include "resolve-undo.h"
 #include "remote.h"
 #include "fmt-merge-msg.h"
@@ -88,6 +89,7 @@ static int no_verify;
 static struct strategy all_strategy[] = {
 	{ "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
 	{ "octopus",    DEFAULT_OCTOPUS },
+	{ "ort",        NO_TRIVIAL },
 	{ "resolve",    0 },
 	{ "ours",       NO_FAST_FORWARD | NO_TRIVIAL },
 	{ "subtree",    NO_FAST_FORWARD | NO_TRIVIAL },
@@ -159,10 +161,17 @@ static struct strategy *get_strategy(const char *name)
 	struct strategy *ret;
 	static struct cmdnames main_cmds, other_cmds;
 	static int loaded;
+	char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
 
 	if (!name)
 		return NULL;
 
+	if (default_strategy &&
+	    !strcmp(default_strategy, "ort") &&
+	    !strcmp(name, "recursive")) {
+		name = "ort";
+	}
+
 	for (i = 0; i < ARRAY_SIZE(all_strategy); i++)
 		if (!strcmp(name, all_strategy[i].name))
 			return &all_strategy[i];
@@ -701,7 +710,8 @@ static int try_merge_strategy(const char *strategy, struct commit_list *common,
 	if (refresh_and_write_cache(REFRESH_QUIET, SKIP_IF_UNCHANGED, 0) < 0)
 		return error(_("Unable to write index."));
 
-	if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree")) {
+	if (!strcmp(strategy, "recursive") || !strcmp(strategy, "subtree") ||
+	    !strcmp(strategy, "ort")) {
 		struct lock_file lock = LOCK_INIT;
 		int clean, x;
 		struct commit *result;
@@ -732,8 +742,12 @@ static int try_merge_strategy(const char *strategy, struct commit_list *common,
 			commit_list_insert(j->item, &reversed);
 
 		hold_locked_index(&lock, LOCK_DIE_ON_ERROR);
-		clean = merge_recursive(&o, head,
-				remoteheads->item, reversed, &result);
+		if (!strcmp(strategy, "ort"))
+			clean = merge_ort_recursive(&o, head, remoteheads->item,
+						    reversed, &result);
+		else
+			clean = merge_recursive(&o, head, remoteheads->item,
+						reversed, &result);
 		if (clean < 0)
 			exit(128);
 		if (write_locked_index(&the_index, &lock,
@@ -1264,6 +1278,12 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	if (branch)
 		skip_prefix(branch, "refs/heads/", &branch);
 
+	if (!pull_twohead) {
+		char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
+		if (default_strategy && !strcmp(default_strategy, "ort"))
+			pull_twohead = "ort";
+	}
+
 	init_diff_ui_defaults();
 	git_config(git_merge_config, NULL);
 

builtin/rebase.c

@@ -119,6 +119,7 @@ static struct replay_opts get_replay_opts(const struct rebase_options *opts)
 	struct replay_opts replay = REPLAY_OPTS_INIT;
 
 	replay.action = REPLAY_INTERACTIVE_REBASE;
+	replay.strategy = NULL;
 	sequencer_init_config(&replay);
 
 	replay.signoff = opts->signoff;
@@ -136,7 +137,12 @@ static struct replay_opts get_replay_opts(const struct rebase_options *opts)
 					opts->committer_date_is_author_date;
 	replay.ignore_date = opts->ignore_date;
 	replay.gpg_sign = xstrdup_or_null(opts->gpg_sign_opt);
-	replay.strategy = opts->strategy;
+	if (opts->strategy)
+		replay.strategy = opts->strategy;
+	else if (!replay.strategy && replay.default_strategy) {
+		replay.strategy = replay.default_strategy;
+		replay.default_strategy = NULL;
+	}
 
 	if (opts->strategy_opts)
 		parse_strategy_opts(&replay, opts->strategy_opts);
@@ -1771,6 +1777,11 @@ int cmd_rebase(int argc, const char **argv, const char *prefix)
 			    options.default_backend);
 	}
 
+	if (options.type == REBASE_MERGE &&
+	    !options.strategy &&
+	    getenv("GIT_TEST_MERGE_ALGORITHM"))
+		options.strategy = xstrdup(getenv("GIT_TEST_MERGE_ALGORITHM"));
+
 	switch (options.type) {
 	case REBASE_MERGE:
 	case REBASE_PRESERVE_MERGES:

builtin/revert.c

@@ -172,6 +172,11 @@ static int run_sequencer(int argc, const char **argv, struct replay_opts *opts)
 				NULL);
 	}
 
+	if (!opts->strategy && opts->default_strategy) {
+		opts->strategy = opts->default_strategy;
+		opts->default_strategy = NULL;
+	}
+
 	if (opts->allow_ff)
 		verify_opt_compatible(me, "--ff",
 				"--signoff", opts->signoff,
@@ -202,6 +207,8 @@ static int run_sequencer(int argc, const char **argv, struct replay_opts *opts)
 	/* These option values will be free()d */
 	opts->gpg_sign = xstrdup_or_null(opts->gpg_sign);
 	opts->strategy = xstrdup_or_null(opts->strategy);
+	if (!opts->strategy && getenv("GIT_TEST_MERGE_ALGORITHM"))
+		opts->strategy = xstrdup(getenv("GIT_TEST_MERGE_ALGORITHM"));
 
 	if (cmd == 'q') {
 		int ret = sequencer_remove_state(opts);

merge-ort-wrappers.c

@@ -0,0 +1,62 @@
+#include "cache.h"
+#include "merge-ort.h"
+#include "merge-ort-wrappers.h"
+
+#include "commit.h"
+
+static int unclean(struct merge_options *opt, struct tree *head)
+{
+	/* Sanity check on repo state; index must match head */
+	struct strbuf sb = STRBUF_INIT;
+
+	if (head && repo_index_has_changes(opt->repo, head, &sb)) {
+		fprintf(stderr, _("Your local changes to the following files would be overwritten by merge:\n  %s"),
+		    sb.buf);
+		strbuf_release(&sb);
+		return -1;
+	}
+
+	return 0;
+}
+
+int merge_ort_nonrecursive(struct merge_options *opt,
+			   struct tree *head,
+			   struct tree *merge,
+			   struct tree *merge_base)
+{
+	struct merge_result result;
+
+	if (unclean(opt, head))
+		return -1;
+
+	if (oideq(&merge_base->object.oid, &merge->object.oid)) {
+		printf(_("Already up to date!"));
+		return 1;
+	}
+
+	memset(&result, 0, sizeof(result));
+	merge_incore_nonrecursive(opt, merge_base, head, merge, &result);
+	merge_switch_to_result(opt, head, &result, 1, 1);
+
+	return result.clean;
+}
+
+int merge_ort_recursive(struct merge_options *opt,
+			struct commit *side1,
+			struct commit *side2,
+			struct commit_list *merge_bases,
+			struct commit **result)
+{
+	struct tree *head = repo_get_commit_tree(opt->repo, side1);
+	struct merge_result tmp;
+
+	if (unclean(opt, head))
+		return -1;
+
+	memset(&tmp, 0, sizeof(tmp));
+	merge_incore_recursive(opt, merge_bases, side1, side2, &tmp);
+	merge_switch_to_result(opt, head, &tmp, 1, 1);
+	*result = NULL;
+
+	return tmp.clean;
+}

merge-ort-wrappers.h

@@ -0,0 +1,25 @@
+#ifndef MERGE_ORT_WRAPPERS_H
+#define MERGE_ORT_WRAPPERS_H
+
+#include "merge-recursive.h"
+
+/*
+ * rename-detecting three-way merge, no recursion.
+ * Wrapper mimicking the old merge_trees() function.
+ */
+int merge_ort_nonrecursive(struct merge_options *opt,
+			   struct tree *head,
+			   struct tree *merge,
+			   struct tree *common);
+
+/*
+ * rename-detecting three-way merge with recursive ancestor consolidation.
+ * Wrapper mimicking the old merge_recursive() function.
+ */
+int merge_ort_recursive(struct merge_options *opt,
+			struct commit *h1,
+			struct commit *h2,
+			struct commit_list *ancestors,
+			struct commit **result);
+
+#endif

merge-ort.c

@@ -0,0 +1,52 @@
+/*
+ * "Ostensibly Recursive's Twin" merge strategy, or "ort" for short.  Meant
+ * as a drop-in replacement for the "recursive" merge strategy, allowing one
+ * to replace
+ *
+ *   git merge [-s recursive]
+ *
+ * with
+ *
+ *   git merge -s ort
+ *
+ * Note: git's parser allows the space between '-s' and its argument to be
+ * missing.  (Should I have backronymed "ham", "alsa", "kip", "nap, "alvo",
+ * "cale", "peedy", or "ins" instead of "ort"?)
+ */
+
+#include "cache.h"
+#include "merge-ort.h"
+
+void merge_switch_to_result(struct merge_options *opt,
+			    struct tree *head,
+			    struct merge_result *result,
+			    int update_worktree_and_index,
+			    int display_update_msgs)
+{
+	die("Not yet implemented");
+	merge_finalize(opt, result);
+}
+
+void merge_finalize(struct merge_options *opt,
+		    struct merge_result *result)
+{
+	die("Not yet implemented");
+}
+
+void merge_incore_nonrecursive(struct merge_options *opt,
+			       struct tree *merge_base,
+			       struct tree *side1,
+			       struct tree *side2,
+			       struct merge_result *result)
+{
+	die("Not yet implemented");
+}
+
+void merge_incore_recursive(struct merge_options *opt,
+			    struct commit_list *merge_bases,
+			    struct commit *side1,
+			    struct commit *side2,
+			    struct merge_result *result)
+{
+	die("Not yet implemented");
+}

merge-ort.h

@@ -0,0 +1,58 @@
+#ifndef MERGE_ORT_H
+#define MERGE_ORT_H
+
+#include "merge-recursive.h"
+
+struct commit;
+struct tree;
+
+struct merge_result {
+	/* Whether the merge is clean */
+	int clean;
+
+	/*
+	 * Result of merge.  If !clean, represents what would go in worktree
+	 * (thus possibly including files containing conflict markers).
+	 */
+	struct tree *tree;
+
+	/*
+	 * Additional metadata used by merge_switch_to_result() or future calls
+	 * to merge_incore_*().  Includes data needed to update the index (if
+	 * !clean) and to print "CONFLICT" messages.  Not for external use.
+	 */
+	void *priv;
+};
+
+/*
+ * rename-detecting three-way merge with recursive ancestor consolidation.
+ * working tree and index are untouched.
+ */
+void merge_incore_recursive(struct merge_options *opt,
+			    struct commit_list *merge_bases,
+			    struct commit *side1,
+			    struct commit *side2,
+			    struct merge_result *result);
+
+/*
+ * rename-detecting three-way merge, no recursion.
+ * working tree and index are untouched.
+ */
+void merge_incore_nonrecursive(struct merge_options *opt,
+			       struct tree *merge_base,
+			       struct tree *side1,
+			       struct tree *side2,
+			       struct merge_result *result);
+
+/* Update the working tree and index from head to result after incore merge */
+void merge_switch_to_result(struct merge_options *opt,
+			    struct tree *head,
+			    struct merge_result *result,
+			    int update_worktree_and_index,
+			    int display_update_msgs);
+
+/* Do needed cleanup when not calling merge_switch_to_result() */
+void merge_finalize(struct merge_options *opt,
+		    struct merge_result *result);
+
+#endif