Merge branch 'jc/strbuf-getline'

The preliminary clean-up for jc/peace-with-crlf topic.

* jc/strbuf-getline:
  strbuf: give strbuf_getline() to the "most text friendly" variant
  checkout-index: there are only two possible line terminations
  update-index: there are only two possible line terminations
  check-ignore: there are only two possible line terminations
  check-attr: there are only two possible line terminations
  mktree: there are only two possible line terminations
  strbuf: introduce strbuf_getline_{lf,nul}()
  strbuf: make strbuf_getline_crlf() global
  strbuf: miniscule style fix

strbuf.h

@@ -354,8 +354,8 @@ extern void strbuf_addftime(struct strbuf *sb, const char *fmt, const struct tm
  *
  * NOTE: The buffer is rewound if the read fails. If -1 is returned,
  * `errno` must be consulted, like you would do for `read(3)`.
- * `strbuf_read()`, `strbuf_read_file()` and `strbuf_getline()` has the
- * same behaviour as well.
+ * `strbuf_read()`, `strbuf_read_file()` and `strbuf_getline_*()`
+ * family of functions have the same behaviour as well.
  */
 extern size_t strbuf_fread(struct strbuf *, size_t, FILE *);
 
@@ -387,14 +387,31 @@ extern ssize_t strbuf_read_file(struct strbuf *sb, const char *path, size_t hint
 extern int strbuf_readlink(struct strbuf *sb, const char *path, size_t hint);
 
 /**
- * Read a line from a FILE *, overwriting the existing contents
- * of the strbuf. The second argument specifies the line
- * terminator character, typically `'\n'`.
+ * Read a line from a FILE *, overwriting the existing contents of
+ * the strbuf.  The strbuf_getline*() family of functions share
+ * this signature, but have different line termination conventions.
+ *
  * Reading stops after the terminator or at EOF.  The terminator
  * is removed from the buffer before returning.  Returns 0 unless
  * there was nothing left before EOF, in which case it returns `EOF`.
  */
-extern int strbuf_getline(struct strbuf *, FILE *, int);
+typedef int (*strbuf_getline_fn)(struct strbuf *, FILE *);
+
+/* Uses LF as the line terminator */
+extern int strbuf_getline_lf(struct strbuf *sb, FILE *fp);
+
+/* Uses NUL as the line terminator */
+extern int strbuf_getline_nul(struct strbuf *sb, FILE *fp);
+
+/*
+ * Similar to strbuf_getline_lf(), but additionally treats a CR that
+ * comes immediately before the LF as part of the terminator.
+ * This is the most friendly version to be used to read "text" files
+ * that can come from platforms whose native text format is CRLF
+ * terminated.
+ */
+extern int strbuf_getline(struct strbuf *, FILE *);
+
 
 /**
  * Like `strbuf_getline`, but keeps the trailing terminator (if