Merge branch 'en/merge-recursive-debug'

Remove remnants of the recursive merge strategy backend, which was
superseded by the ort merge strategy.

* en/merge-recursive-debug:
  builtin/{merge,rebase,revert}: remove GIT_TEST_MERGE_ALGORITHM
  tests: remove GIT_TEST_MERGE_ALGORITHM and test_expect_merge_algorithm
  merge-recursive.[ch]: thoroughly debug these
  merge, sequencer: switch recursive merges over to ort
  sequencer: switch non-recursive merges over to ort
  merge-ort: enable diff-algorithms other than histogram
  builtin/merge-recursive: switch to using merge_ort_generic()
  checkout: replace merge_trees() with merge_ort_nonrecursive()

Author: gitster

Documentation/merge-strategies.adoc

@@ -87,44 +87,33 @@ no-renames;;
 	configuration variable.
 	See also linkgit:git-diff[1] `--no-renames`.
 
-subtree[=<path>];;
-	This option is a more advanced form of 'subtree' strategy, where
-	the strategy makes a guess on how two trees must be shifted to
-	match with each other when merging.  Instead, the specified path
-	is prefixed (or stripped from the beginning) to make the shape of
-	two trees to match.
-
-recursive::
-	This can only resolve two heads using a 3-way merge
-	algorithm.  When there is more than one common
-	ancestor that can be used for 3-way merge, it creates a
-	merged tree of the common ancestors and uses that as
-	the reference tree for the 3-way merge.  This has been
-	reported to result in fewer merge conflicts without
-	causing mismerges by tests done on actual merge commits
-	taken from Linux 2.6 kernel development history.
-	Additionally this can detect and handle merges involving
-	renames.  It does not make use of detected copies.  This was
-	the default strategy for resolving two heads from Git v0.99.9k
-	until v2.33.0.
-+
-For a path that is a submodule, the same caution as 'ort' applies to this
-strategy.
-+
-The 'recursive' strategy takes the same options as 'ort'.  However,
-there are two additional options that 'ort' ignores (not documented
-above) that are potentially useful with the 'recursive' strategy:
+histogram;;
+	Deprecated synonym for `diff-algorithm=histogram`.
 
 patience;;
 	Deprecated synonym for `diff-algorithm=patience`.
 
-diff-algorithm=[patience|minimal|histogram|myers];;
+diff-algorithm=[histogram|minimal|myers|patience];;
 	Use a different diff algorithm while merging, which can help
 	avoid mismerges that occur due to unimportant matching lines
 	(such as braces from distinct functions).  See also
 	linkgit:git-diff[1] `--diff-algorithm`.  Note that `ort`
-	specifically uses `diff-algorithm=histogram`, while `recursive`
-	defaults to the `diff.algorithm` config setting.
+	defaults to `diff-algorithm=histogram`, while regular diffs
+	currently default to the `diff.algorithm` config setting.
+
+subtree[=<path>];;
+	This option is a more advanced form of 'subtree' strategy, where
+	the strategy makes a guess on how two trees must be shifted to
+	match with each other when merging.  Instead, the specified path
+	is prefixed (or stripped from the beginning) to make the shape of
+	two trees to match.
+
+recursive::
+	This is now a synonym for `ort`.  It was an alternative
+	implementation until v2.49.0, but was redirected to mean `ort`
+	in v2.50.0.  The previous recursive strategy was the default
+	strategy for resolving two heads from Git v0.99.9k until
+	v2.33.0.
 
 resolve::
 	This can only resolve two heads (i.e. the current branch
@@ -145,7 +134,7 @@ ours::
 	ignoring all changes from all other branches.  It is meant to
 	be used to supersede old development history of side
 	branches.  Note that this is different from the -Xours option to
-	the 'recursive' merge strategy.
+	the 'ort' merge strategy.
 
 subtree::
 	This is a modified `ort` strategy. When merging trees A and

Documentation/technical/sparse-checkout.adoc

@@ -356,8 +356,6 @@ understanding these differences can be beneficial.
     The behavior for these commands somewhat depends upon the merge
     strategy being used:
       * `ort` behaves as described above
-      * `recursive` tries to not vivify files unnecessarily, but does sometimes
-	vivify files without conflicts.
       * `octopus` and `resolve` will always vivify any file changed in the merge
 	relative to the first parent, which is rather suboptimal.
 

Makefile

@@ -1070,7 +1070,6 @@ LIB_OBJS += merge-blobs.o
 LIB_OBJS += merge-ll.o
 LIB_OBJS += merge-ort.o
 LIB_OBJS += merge-ort-wrappers.o
-LIB_OBJS += merge-recursive.o
 LIB_OBJS += merge.o
 LIB_OBJS += midx.o
 LIB_OBJS += midx-write.o

builtin/checkout.c

@@ -17,7 +17,7 @@
 #include "merge-ll.h"
 #include "lockfile.h"
 #include "mem-pool.h"
-#include "merge-recursive.h"
+#include "merge-ort-wrappers.h"
 #include "object-name.h"
 #include "object-store-ll.h"
 #include "parse-options.h"
@@ -907,10 +907,10 @@ static int merge_working_tree(const struct checkout_opts *opts,
 			o.branch1 = new_branch_info->name;
 			o.branch2 = "local";
 			o.conflict_style = opts->conflict_style;
-			ret = merge_trees(&o,
-					  new_tree,
-					  work,
-					  old_tree);
+			ret = merge_ort_nonrecursive(&o,
+						     new_tree,
+						     work,
+						     old_tree);
 			if (ret < 0)
 				exit(128);
 			ret = reset_tree(new_tree,

builtin/merge-recursive.c

@@ -3,7 +3,7 @@
 #include "advice.h"
 #include "gettext.h"
 #include "hash.h"
-#include "merge-recursive.h"
+#include "merge-ort-wrappers.h"
 #include "object-name.h"
 
 static const char builtin_merge_recursive_usage[] =
@@ -89,7 +89,7 @@ int cmd_merge_recursive(int argc,
 	if (o.verbosity >= 3)
 		printf(_("Merging %s with %s\n"), o.branch1, o.branch2);
 
-	failed = merge_recursive_generic(&o, &h1, &h2, bases_count, bases, &result);
+	failed = merge_ort_generic(&o, &h1, &h2, bases_count, bases, &result);
 
 	free(better1);
 	free(better2);

builtin/merge.c

@@ -39,7 +39,6 @@
 #include "rerere.h"
 #include "help.h"
 #include "merge.h"
-#include "merge-recursive.h"
 #include "merge-ort-wrappers.h"
 #include "resolve-undo.h"
 #include "remote.h"
@@ -171,7 +170,7 @@ static struct strategy *get_strategy(const char *name)
 	struct strategy *ret;
 	static struct cmdnames main_cmds = {0}, other_cmds = {0};
 	static int loaded;
-	char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
+	char *default_strategy = NULL;
 
 	if (!name)
 		return NULL;
@@ -750,12 +749,8 @@ static int try_merge_strategy(const char *strategy, struct commit_list *common,
 
 		repo_hold_locked_index(the_repository, &lock,
 				       LOCK_DIE_ON_ERROR);
-		if (!strcmp(strategy, "ort"))
-			clean = merge_ort_recursive(&o, head, remoteheads->item,
-						    reversed, &result);
-		else
-			clean = merge_recursive(&o, head, remoteheads->item,
-						reversed, &result);
+		clean = merge_ort_recursive(&o, head, remoteheads->item,
+					    reversed, &result);
 		free_commit_list(reversed);
 		strbuf_release(&o.obuf);
 
@@ -1316,12 +1311,6 @@ int cmd_merge(int argc,
 	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 = xstrdup("ort");
-	}
-
 	init_diff_ui_defaults();
 	git_config(git_merge_config, NULL);
 
@@ -1522,12 +1511,6 @@ int cmd_merge(int argc,
 			fast_forward = FF_NO;
 	}
 
-	if (!use_strategies && !pull_twohead &&
-	    remoteheads && !remoteheads->next) {
-		char *default_strategy = getenv("GIT_TEST_MERGE_ALGORITHM");
-		if (default_strategy)
-			append_strategy(get_strategy(default_strategy));
-	}
 	if (!use_strategies) {
 		if (!remoteheads)
 			; /* already up-to-date */

builtin/rebase.c

@@ -1575,11 +1575,6 @@ int cmd_rebase(int argc,
 			    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:
 		options.state_dir = merge_dir();

builtin/revert.c

@@ -252,8 +252,6 @@ static int run_sequencer(int argc, const char **argv, const char *prefix,
 		free(opts->strategy);
 		opts->strategy = xstrdup_or_null(strategy);
 	}
-	if (!opts->strategy && getenv("GIT_TEST_MERGE_ALGORITHM"))
-		opts->strategy = xstrdup(getenv("GIT_TEST_MERGE_ALGORITHM"));
 	free(options);
 
 	if (cmd == 'q') {

ci/run-build-and-tests.sh

@@ -20,7 +20,6 @@ linux-breaking-changes)
 linux-TEST-vars)
 	export OPENSSL_SHA1_UNSAFE=YesPlease
 	export GIT_TEST_SPLIT_INDEX=yes
-	export GIT_TEST_MERGE_ALGORITHM=recursive
 	export GIT_TEST_FULL_IN_PACK_ARRAY=true
 	export GIT_TEST_OE_SIZE=10
 	export GIT_TEST_OE_DELTA_SIZE=5

merge-ort-wrappers.h

@@ -1,7 +1,7 @@
 #ifndef MERGE_ORT_WRAPPERS_H
 #define MERGE_ORT_WRAPPERS_H
 
-#include "merge-recursive.h"
+#include "merge-ort.h"
 
 /*
  * rename-detecting three-way merge, no recursion.