[PATCH v16 7/7] branch: add --dry-run for --delete-merged

["Harald Nordgren via GitGitGadget" <gitgitgadget@gmail.com>]

From: Harald Nordgren <haraldnordgren@gmail.com>

With --dry-run, --delete-merged prints the local branches it would
delete, one "Would delete branch <name>" line each, and exits
without touching any ref. The same filtering applies, so the output
is exactly the set that the real run would delete.

--dry-run is only meaningful together with --delete-merged and is
rejected otherwise.

Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
---
 Documentation/git-branch.adoc |  8 +++++++-
 builtin/branch.c              |  9 ++++++++-
 t/t3200-branch.sh             | 11 ++++++++++-
 3 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/Documentation/git-branch.adoc b/Documentation/git-branch.adoc
index 91700f2e8a..09063d74f2 100644
--- a/Documentation/git-branch.adoc
+++ b/Documentation/git-branch.adoc
@@ -25,7 +25,7 @@ git branch (-m|-M) [<old-branch>] <new-branch>
 git branch (-c|-C) [<old-branch>] <new-branch>
 git branch (-d|-D) [-r] <branch-name>...
 git branch --edit-description [<branch-name>]
-git branch --delete-merged <branch>...
+git branch [--dry-run] --delete-merged <branch>...
 
 DESCRIPTION
 -----------
@@ -226,6 +226,12 @@ A branch whose work has not yet been merged into its upstream is
 silently skipped. Delete it with `git branch -D` if you want to
 remove it anyway.
 
+`--dry-run`::
+	With `--delete-merged`, print which branches would be
+	deleted and exit without touching any ref.  Useful for
+	sanity-checking a wide pattern like `'origin/*'` before
+	committing to the deletion.
+
 `-v`::
 `-vv`::
 `--verbose`::
diff --git a/builtin/branch.c b/builtin/branch.c
index 942e2297c8..f67d0949fe 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -826,6 +826,7 @@ int cmd_branch(int argc,
 	int delete = 0, rename = 0, copy = 0, list = 0,
 	    unset_upstream = 0, show_current = 0, edit_description = 0;
 	int delete_merged = 0;
+	int dry_run = 0;
 	const char *new_upstream = NULL;
 	int noncreate_actions = 0;
 	/* possible options */
@@ -881,6 +882,8 @@ int cmd_branch(int argc,
 			 N_("edit the description for the branch")),
 		OPT_BOOL(0, "delete-merged", &delete_merged,
 			N_("delete local branches whose upstream matches <branch> and are merged")),
+		OPT_BOOL(0, "dry-run", &dry_run,
+			N_("with --delete-merged, only print which branches would be deleted")),
 		OPT__FORCE(&force, N_("force creation, move/rename, deletion"), PARSE_OPT_NOCOMPLETE),
 		OPT_MERGED(&filter, N_("print only branches that are merged")),
 		OPT_NO_MERGED(&filter, N_("print only branches that are not merged")),
@@ -943,6 +946,9 @@ int cmd_branch(int argc,
 	if (noncreate_actions > 1)
 		usage_with_options(builtin_branch_usage, options);
 
+	if (dry_run && !delete_merged)
+		die(_("--dry-run requires --delete-merged"));
+
 	if (recurse_submodules_explicit) {
 		if (!submodule_propagate_branches)
 			die(_("branch with --recurse-submodules can only be used if submodule.propagateBranches is enabled"));
@@ -983,7 +989,8 @@ int cmd_branch(int argc,
 		goto out;
 	} else if (delete_merged) {
 		ret = delete_merged_branches(argc, argv,
-					     quiet ? DELETE_BRANCH_QUIET : 0);
+					     (quiet ? DELETE_BRANCH_QUIET : 0) |
+					     (dry_run ? DELETE_BRANCH_DRY_RUN : 0));
 		goto out;
 	} else if (show_current) {
 		print_current_branch_name();
diff --git a/t/t3200-branch.sh b/t/t3200-branch.sh
index 09cecfaff5..4a71845c76 100755
--- a/t/t3200-branch.sh
+++ b/t/t3200-branch.sh
@@ -1892,8 +1892,12 @@ test_expect_success '--delete-merged deletes merged branches and spares the rest
 	) &&
 	sha=$(git -C repo rev-parse --short merged) &&
 
-	git -C repo branch --delete-merged origin/next >actual 2>&1 &&
+	git -C repo branch --dry-run --delete-merged origin/next >actual 2>&1 &&
+	echo "Would delete branch merged (was $sha)." >expect &&
+	test_cmp expect actual &&
+	git -C repo rev-parse --verify refs/heads/merged &&
 
+	git -C repo branch --delete-merged origin/next >actual 2>&1 &&
 	echo "Deleted branch merged (was $sha)." >expect &&
 	test_cmp expect actual &&
 	git -C repo for-each-ref --format="%(refname:short)" refs/heads/ >actual &&
@@ -1970,4 +1974,9 @@ test_expect_success "branch -d still deletes a deleteMerged=false branch" '
 	test_must_fail git -C repo rev-parse --verify refs/heads/kept
 '
 
+test_expect_success '--dry-run without --delete-merged is rejected' '
+	test_must_fail git -C forked branch --dry-run 2>err &&
+	test_grep "requires --delete-merged" err
+'
+
 test_done
-- 
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