[PATCH v2 04/21] die_unterminated_line(), die_invalid_line(): new functions

[Michael Haggerty <mhagger@alum.mit.edu>]

Extract some helper functions for reporting errors. While we're at it,
prevent them from spewing unlimited output to the terminal. These
functions will soon have more callers.

These functions accept the problematic line as a `(ptr, len)` pair
rather than a NUL-terminated string, and `die_invalid_line()` checks
for an EOL itself, because these calling conventions will be
convenient for future callers. (Efficiency is not a concern here
because these functions are only ever called if the `packed-refs` file
is corrupt.)

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 refs/packed-backend.c | 28 +++++++++++++++++++++++++---
 1 file changed, 25 insertions(+), 3 deletions(-)

diff --git a/refs/packed-backend.c b/refs/packed-backend.c
index a3d9210cb0..5c50c223ef 100644
--- a/refs/packed-backend.c
+++ b/refs/packed-backend.c
@@ -161,6 +161,29 @@ static const char *parse_ref_line(struct strbuf *line, struct object_id *oid)
 	return ref;
 }
 
+static NORETURN void die_unterminated_line(const char *path,
+					   const char *p, size_t len)
+{
+	if (len < 80)
+		die("unterminated line in %s: %.*s", path, (int)len, p);
+	else
+		die("unterminated line in %s: %.75s...", path, p);
+}
+
+static NORETURN void die_invalid_line(const char *path,
+				      const char *p, size_t len)
+{
+	const char *eol = memchr(p, '\n', len);
+
+	if (!eol)
+		die_unterminated_line(path, p, len);
+	else if (eol - p < 80)
+		die("unexpected line in %s: %.*s", path, (int)(eol - p), p);
+	else
+		die("unexpected line in %s: %.75s...", path, p);
+
+}
+
 /*
  * Read from the `packed-refs` file into a newly-allocated
  * `packed_ref_cache` and return it. The return value will already
@@ -227,7 +250,7 @@ static struct packed_ref_cache *read_packed_refs(struct packed_ref_store *refs)
 		const char *traits;
 
 		if (!line.len || line.buf[line.len - 1] != '\n')
-			die("unterminated line in %s: %s", refs->path, line.buf);
+			die_unterminated_line(refs->path, line.buf, line.len);
 
 		if (skip_prefix(line.buf, "# pack-refs with:", &traits)) {
 			if (strstr(traits, " fully-peeled "))
@@ -266,8 +289,7 @@ static struct packed_ref_cache *read_packed_refs(struct packed_ref_store *refs)
 			 */
 			last->flag |= REF_KNOWS_PEELED;
 		} else {
-			strbuf_setlen(&line, line.len - 1);
-			die("unexpected line in %s: %s", refs->path, line.buf);
+			die_invalid_line(refs->path, line.buf, line.len);
 		}
 	}
 
-- 
2.14.1