Improves experience during upgrades, accidentally running
an old fish with a new environment. No errors just from
printing a prompt. Fixes#3057.
Print helpful notice also when launching mismatched fish.
Autoloadable string.fish -- only create function if not builtin.
Much better to only encode the characters that are not URL-safe. This
also doesn't involve any forking, and it even handles newlines and NULs
in the input.
* When using a UTF-8 locale, set locale to C temporarily in order to
read one byte at a time.
* Use the builtin printf in a forward-compatible way. (GNU)
* Improve the readability of the code.
