pull: set reflog message

f947413 (Use GIT_REFLOG_ACTION environment variable instead.,
2006-12-28) established git-pull's method for setting the reflog
message, which is to set the environment variable GIT_REFLOG_ACTION to
the evaluation of "pull${1+ $*}" if it has not already been set.

Re-implement this behavior.

Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Paul Tan <pyokagan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/pull.c

@@ -168,6 +168,25 @@ static void argv_push_force(struct argv_array *arr)
 		argv_array_push(arr, "-f");
 }
 
+/**
+ * Sets the GIT_REFLOG_ACTION environment variable to the concatenation of argv
+ */
+static void set_reflog_message(int argc, const char **argv)
+{
+	int i;
+	struct strbuf msg = STRBUF_INIT;
+
+	for (i = 0; i < argc; i++) {
+		if (i)
+			strbuf_addch(&msg, ' ');
+		strbuf_addstr(&msg, argv[i]);
+	}
+
+	setenv("GIT_REFLOG_ACTION", msg.buf, 0);
+
+	strbuf_release(&msg);
+}
+
 /**
  * If pull.ff is unset, returns NULL. If pull.ff is "true", returns "--ff". If
  * pull.ff is "false", returns "--no-ff". If pull.ff is "only", returns
@@ -443,6 +462,9 @@ int cmd_pull(int argc, const char **argv, const char *prefix)
 			die_errno("could not exec %s", path);
 	}
 
+	if (!getenv("GIT_REFLOG_ACTION"))
+		set_reflog_message(argc, argv);
+
 	argc = parse_options(argc, argv, prefix, pull_options, pull_usage, 0);
 
 	parse_repo_refspecs(argc, argv, &repo, &refspecs);