builtin/{merge,rebase,revert}: remove GIT_TEST_MERGE_ALGORITHM

This environment variable existed to allow the testsuite to reuse all
the merge-related tests in the testsuite while easily flipping between
the 'recursive' and the 'ort' backends.  Now that we have removed
merge-recursive and remapped 'recursive' to mean 'ort', we don't need
this scaffolding anymore.  Remove it from these three builtins.

Signed-off-by: Elijah Newren <newren@gmail.com>

Author: newren

Diff for: builtin/merge.c

@@ -170,7 +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;
@@ -1311,12 +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);
 
@@ -1517,12 +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 */

Diff for: 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();

Diff for: 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') {