parse: implement `git_parse_peek`

Some code parts need to inspect the next few bytes without actually
consuming it yet, for example to examine what content it has to expect
next. Create a new function `git_parse_peek` which returns the next byte
without modifying the parsing context and use it at multiple call sites.

1 files changed, 22 insertions, 0 deletions

diff --git a/src/parse.c b/src/parse.c
index 57da1c3cf..c1bd213ec 100644
--- a/src/parse.c
+++ b/src/parse.c
@@ -94,3 +94,25 @@ int git_parse_advance_digit(int64_t *out, git_parse_ctx *ctx, int base)
 	git_parse_advance_chars(ctx, (end - ctx->line));
 	return 0;
 }
+
+int git_parse_peek(char *out, git_parse_ctx *ctx, int flags)
+{
+	size_t remain = ctx->line_len;
+	const char *ptr = ctx->line;
+
+	while (remain) {
+		char c = *ptr;
+
+		if ((flags & GIT_PARSE_PEEK_SKIP_WHITESPACE) &&
+		    git__isspace(c)) {
+			remain--;
+			ptr++;
+			continue;
+		}
+
+		*out = c;
+		return 0;
+	}
+
+	return -1;
+}