templater: strictly parse leading backslashes of '{' (issue4569) (BC) Because double backslashes are processed as a string escape sequence, '\\{' should start the template syntax. On the other hand, r'' disables any sort of \-escapes, so r'\{' can go either way, never start the template syntax or always start it. I simply chose the latter, which means r'\{' is the same as '\\{'.

templater: do not process \-escapes at parsestring() (issue4290) This patch brings back pre-2.8.1 behavior. The result of parsestring() is stored in templater's cache, t.cache, and then it is parsed as a template string by compiletemplate(). So t.cache should keep an unparsed string no matter if it is sourced from config value. Otherwise backslashes would be processed twice. The test vector is borrowed from 64b4f0cd7336.