checkout: change default strategy to SAFE

As per #4200, our default is quite surprising to users that expect checkout to just "do the thing".

CHANGELOG.md

@@ -9,6 +9,8 @@ v0.27 + 1
 
 ### Breaking API changes
 
+* The default checkout strategy changed from `DRY_RUN` to `SAFE` (#4531).
+
 v0.27
 ---------
 

include/git2/checkout.h

@@ -251,7 +251,7 @@ typedef void (*git_checkout_perfdata_cb)(
 typedef struct git_checkout_options {
 	unsigned int version;
 
-	unsigned int checkout_strategy; /**< default will be a dry run */
+	unsigned int checkout_strategy; /**< default will be a safe checkout */
 
 	int disable_filters;    /**< don't apply filters like CRLF conversion */
 	unsigned int dir_mode;  /**< default is 0755 */
@@ -295,7 +295,7 @@ typedef struct git_checkout_options {
 } git_checkout_options;
 
 #define GIT_CHECKOUT_OPTIONS_VERSION 1
-#define GIT_CHECKOUT_OPTIONS_INIT {GIT_CHECKOUT_OPTIONS_VERSION}
+#define GIT_CHECKOUT_OPTIONS_INIT {GIT_CHECKOUT_OPTIONS_VERSION, GIT_CHECKOUT_SAFE}
 
 /**
 * Initializes a `git_checkout_options` with default values. Equivalent to

src/rebase.c

@@ -275,9 +275,6 @@ static int rebase_alloc(git_rebase **out, const git_rebase_options *rebase_opts)
 		GITERR_CHECK_ALLOC(rebase->options.rewrite_notes_ref);
 	}
 
-	if ((rebase->options.checkout_options.checkout_strategy & (GIT_CHECKOUT_SAFE | GIT_CHECKOUT_FORCE)) == 0)
-		rebase->options.checkout_options.checkout_strategy = GIT_CHECKOUT_SAFE;
-
 	*out = rebase;
 
 	return 0;

src/stash.c

@@ -738,9 +738,6 @@ static void normalize_apply_options(
 		memcpy(opts, &default_apply_opts, sizeof(git_stash_apply_options));
 	}
 
-	if ((opts->checkout_options.checkout_strategy & (GIT_CHECKOUT_SAFE | GIT_CHECKOUT_FORCE)) == 0)
-		opts->checkout_options.checkout_strategy = GIT_CHECKOUT_SAFE;
-
 	if (!opts->checkout_options.our_label)
 		opts->checkout_options.our_label = "Updated upstream";