completion: add 'git history' subcommands

Use the parse-options completion helpers for the

  git history

subcommands and their options. All current history subcommands take a
revision as their first positional argument, so complete that argument
as a revision.

Once the revision is present, leave any further positional arguments to
subcommand-specific completion. This allows a subcommand to complete
another kind of argument, such as the pathspec accepted by

  git history split

or another revision if a future subcommand accepts one.

Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -2137,6 +2137,51 @@ _git_help ()
 	fi
 }
 
+__git_history_has_revision ()
+{
+	local i
+
+	for ((i = __git_cmd_idx + 2; i < cword; i++)); do
+		case "${words[i]}" in
+		-*)
+			;;
+		*)
+			return 0
+			;;
+		esac
+	done
+	return 1
+}
+
+_git_history ()
+{
+	local subcommands subcommand
+
+	__git_resolve_builtins "history"
+
+	subcommands="$___git_resolved_builtins"
+	subcommand="$(__git_find_subcommand "$subcommands")"
+
+	if [ -z "$subcommand" ]; then
+		__gitcomp "$subcommands"
+		return
+	fi
+
+	if ! __git_has_doubledash; then
+		case "$cur" in
+		--*)
+			__gitcomp_builtin "history_$subcommand"
+			return
+			;;
+		esac
+	fi
+
+	if ! __git_history_has_revision; then
+		__git_complete_refs
+		return
+	fi
+}
+
 _git_init ()
 {
 	case "$cur" in

t/t9902-completion.sh

@@ -3107,6 +3107,36 @@ test_expect_success 'git clone --config= - value' '
 	EOF
 '
 
+test_expect_success 'git history subcommands' '
+	test_completion "git history " <<-\EOF &&
+	drop Z
+	fixup Z
+	reword Z
+	split Z
+	EOF
+	test_completion "git history --" ""
+'
+
+test_expect_success 'git history subcommand options' '
+	test_completion "git history split main --" <<-\EOF &&
+	--update-refs=Z
+	--dry-run Z
+	--no-dry-run Z
+	EOF
+	test_completion "git history fixup --upd" "--update-refs=" &&
+	test_completion "git history fixup --ree" "--reedit-message " &&
+	test_completion "git history split --upd" "--update-refs=" &&
+	test_completion "git history split main --dry" "--dry-run " &&
+	test_completion "git history reword main -- --d" ""
+'
+
+test_expect_success 'git history revisions' '
+	test_completion "git history split ma" "main " &&
+	test_completion "git history split --update-refs=head ma" "main " &&
+	test_completion "git history fixup --empty=drop ma" "main " &&
+	test_completion "git history reword main m" ""
+'
+
 test_expect_success 'git reflog show' '
 	test_when_finished "git checkout - && git branch -d shown" &&
 	git checkout -b shown &&