Merge branch 'jk/core-comment-string'

core.commentChar used to be limited to a single byte, but has been
updated to allow an arbitrary multi-byte sequence.

* jk/core-comment-string:
  config: add core.commentString
  config: allow multi-byte core.commentChar
  environment: drop comment_line_char compatibility macro
  wt-status: drop custom comment-char stringification
  sequencer: handle multi-byte comment characters when writing todo list
  find multi-byte comment chars in unterminated buffers
  find multi-byte comment chars in NUL-terminated strings
  prefer comment_line_str to comment_line_char for printing
  strbuf: accept a comment string for strbuf_add_commented_lines()
  strbuf: accept a comment string for strbuf_commented_addf()
  strbuf: accept a comment string for strbuf_stripspace()
  environment: store comment_line_char as a string
  strbuf: avoid shadowing global comment_line_char name
  commit: refactor base-case of adjust_comment_line_char()
  strbuf: avoid static variables in strbuf_add_commented_lines()
  strbuf: simplify comment-handling in add_lines() helper
  config: forbid newline as core.commentChar

environment.c

@@ -110,7 +110,7 @@ int protect_ntfs = PROTECT_NTFS_DEFAULT;
  * The character that begins a commented line in user-editable file
  * that is subject to stripspace.
  */
-char comment_line_char = '#';
+const char *comment_line_str = "#";
 int auto_comment_line_char;
 
 /* Parallel index stat data preload? */