[PATCH v14 3/6] branch: prepare delete_branches for a bulk caller

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

From: Harald Nordgren <haraldnordgren@gmail.com>

Teach delete_branches() two new modes for the upcoming
--prune-merged: one that asks only whether a branch is merged into
its upstream, without falling back to HEAD when there is no
upstream, and one that rehearses the deletions without removing any
ref. Existing callers keep their current behavior.

Signed-off-by: Harald Nordgren <haraldnordgren@gmail.com>
---
 builtin/branch.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/builtin/branch.c b/builtin/branch.c
index 4fb012c7a4..2cc5a8cde0 100644
--- a/builtin/branch.c
+++ b/builtin/branch.c
@@ -168,10 +168,13 @@ static int branch_merged(int kind, const char *name,
 	 * upstream, if any, otherwise with HEAD", we should just
 	 * return the result of the repo_in_merge_bases() above without
 	 * any of the following code, but during the transition period,
-	 * a gentle reminder is in order.
+	 * a gentle reminder is in order.  Callers that opt out of the
+	 * HEAD fallback by passing head_rev=NULL are not interested in
+	 * the reminder either: they have already established that the
+	 * branch has an upstream, so HEAD is irrelevant to the decision.
 	 */
-	if (head_rev != reference_rev) {
-		int expect = head_rev ? repo_in_merge_bases(the_repository, rev, head_rev) : 0;
+	if (head_rev && head_rev != reference_rev) {
+		int expect = repo_in_merge_bases(the_repository, rev, head_rev);
 		if (expect < 0)
 			exit(128);
 		if (expect == merged)
@@ -193,6 +196,8 @@ enum delete_branch_flags {
 	DELETE_BRANCH_FORCE = (1 << 0),
 	DELETE_BRANCH_QUIET = (1 << 1),
 	DELETE_BRANCH_WARN_ONLY = (1 << 2),
+	DELETE_BRANCH_NO_HEAD_FALLBACK = (1 << 3),
+	DELETE_BRANCH_DRY_RUN = (1 << 4),
 };
 
 static int check_branch_commit(const char *branchname, const char *refname,
@@ -240,7 +245,7 @@ static int delete_branches(int argc, const char **argv, int kinds,
 	int i;
 	int ret = 0;
 	int remote_branch = 0;
-	int force, quiet;
+	int force, quiet, dry_run, no_head_fallback;
 	struct strbuf bname = STRBUF_INIT;
 	enum interpret_branch_kind allowed_interpret;
 	struct string_list refs_to_delete = STRING_LIST_INIT_DUP;
@@ -268,8 +273,10 @@ static int delete_branches(int argc, const char **argv, int kinds,
 
 	force = flags & DELETE_BRANCH_FORCE;
 	quiet = flags & DELETE_BRANCH_QUIET;
+	dry_run = flags & DELETE_BRANCH_DRY_RUN;
+	no_head_fallback = flags & DELETE_BRANCH_NO_HEAD_FALLBACK;
 
-	if (!force)
+	if (!force && !no_head_fallback)
 		head_rev = lookup_commit_reference(the_repository, &head_oid);
 
 	for (i = 0; i < argc; i++, strbuf_reset(&bname)) {
@@ -340,13 +347,20 @@ static int delete_branches(int argc, const char **argv, int kinds,
 		free(target);
 	}
 
-	if (refs_delete_refs(get_main_ref_store(the_repository), NULL, &refs_to_delete, REF_NO_DEREF))
+	if (!dry_run &&
+	    refs_delete_refs(get_main_ref_store(the_repository), NULL, &refs_to_delete, REF_NO_DEREF))
 		ret = 1;
 
 	for_each_string_list_item(item, &refs_to_delete) {
 		char *describe_ref = item->util;
 		char *name = item->string;
-		if (!refs_ref_exists(get_main_ref_store(the_repository), name)) {
+		if (dry_run) {
+			if (!quiet)
+				printf(remote_branch
+					? _("Would delete remote-tracking branch %s (was %s).\n")
+					: _("Would delete branch %s (was %s).\n"),
+					name + branch_name_pos, describe_ref);
+		} else if (!refs_ref_exists(get_main_ref_store(the_repository), name)) {
 			char *refname = name + branch_name_pos;
 			if (!quiet)
 				printf(remote_branch
-- 
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