fetch --prune: Run prune before fetching

When we have a remote-tracking branch named "frotz/nitfol" from a
previous fetch, and the upstream now has a branch named "frotz",
fetch would fail to remove "frotz/nitfol" with a "git fetch --prune"
from the upstream. git would inform the user to use "git remote
prune" to fix the problem.

Change the way "fetch --prune" works by moving the pruning operation
before the fetching operation. This way, instead of warning the user
of a conflict, it autmatically fixes it.

Signed-off-by: Tom Miller <jackerran@gmail.com>
Tested-by: Thomas Rast <tr@thomasrast.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/fetch.c

@@ -863,11 +863,6 @@ static int do_fetch(struct transport *transport,
 
 	if (tags == TAGS_DEFAULT && autotags)
 		transport_set_option(transport, TRANS_OPT_FOLLOWTAGS, "1");
-	if (fetch_refs(transport, ref_map)) {
-		free_refs(ref_map);
-		retcode = 1;
-		goto cleanup;
-	}
 	if (prune) {
 		/*
 		 * We only prune based on refspecs specified
@@ -883,6 +878,11 @@ static int do_fetch(struct transport *transport,
 				   transport->url);
 		}
 	}
+	if (fetch_refs(transport, ref_map)) {
+		free_refs(ref_map);
+		retcode = 1;
+		goto cleanup;
+	}
 	free_refs(ref_map);
 
 	/* if neither --no-tags nor --tags was specified, do automated tag

t/t5510-fetch.sh

@@ -626,4 +626,18 @@ test_expect_success 'fetch --prune prints the remotes url' '
 	test_cmp expect actual
 '
 
+test_expect_success 'branchname D/F conflict resolved by --prune' '
+	git branch dir/file &&
+	git clone . prune-df-conflict &&
+	git branch -D dir/file &&
+	git branch dir &&
+	(
+		cd prune-df-conflict &&
+		git fetch --prune &&
+		git rev-parse origin/dir >../actual
+	) &&
+	git rev-parse dir >expect &&
+	test_cmp expect actual
+'
+
 test_done