[PATCH v2 2/3] sequencer: factor out todo command name parsing

["Phillip Wood via GitGitGadget" <gitgitgadget@gmail.com>]

From: Phillip Wood <phillip.wood@dunelm.org.uk>

Factor out the code that parses the name of the command at the start of
each line in the todo file into its own function so that it can be used
in the next commit.

As I don't want to burden other callers with having to pass in a pointer
to the end of the line the test for an abbreviated command is
changed. This change should not affect the behavior. Instead of testing
`eol == bol + 1` the new code checks for the end of the line by testing
for '\n', '\r' or '\0' following the abbreviated name. To avoid reading
past the end of an empty string it also checks that there is actually a
single character abbreviation before testing if it matches. This
prevents it from matching '\0' as the abbreviated name and then trying
to read another character.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
---
 sequencer.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/sequencer.c b/sequencer.c
index 919e3153f5..793f86bf9a 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -2076,6 +2076,18 @@ const char *todo_item_get_arg(struct todo_list *todo_list,
 	return todo_list->buf.buf + item->arg_offset;
 }
 
+static int is_command(enum todo_command command, const char **bol)
+{
+	const char *str = todo_command_info[command].str;
+	const char nick = todo_command_info[command].c;
+	const char *p = *bol + 1;
+
+	return skip_prefix(*bol, str, bol) ||
+		((nick && **bol == nick) &&
+		 (*p == ' ' || *p == '\t' || *p == '\n' || *p == '\r' || !*p) &&
+		 (*bol = p));
+}
+
 static int parse_insn_line(struct repository *r, struct todo_item *item,
 			   const char *buf, const char *bol, char *eol)
 {
@@ -2097,12 +2109,7 @@ static int parse_insn_line(struct repository *r, struct todo_item *item,
 	}
 
 	for (i = 0; i < TODO_COMMENT; i++)
-		if (skip_prefix(bol, todo_command_info[i].str, &bol)) {
-			item->command = i;
-			break;
-		} else if ((bol + 1 == eol || bol[1] == ' ' || bol[1] == '\t') &&
-			   *bol == todo_command_info[i].c) {
-			bol++;
+		if (is_command(i, &bol)) {
 			item->command = i;
 			break;
 		}
-- 
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