[PATCH 2/2] Split bash compatible extensions into separate options.

[Denys Vlasenko]

On Tue, Jan 10, 2017 at 8:17 PM, Kang-Che Sung <explorer09 at gmail.com> wrote:
> All of the bash compatibility options will now depend on
> CONFIG_*_BASH_COMPAT, and CONFIG_*_BASH_COMPAT become an option that
> alone doesn't add any code.
>
> Splitting these options allows more flexibility in configuration

Configuration shouldn't strive to be maximally flexible.

It floods the user with way too many options.
For example, now LS has eight suboptions.
Imagine this instead:

[*] ls
[*]   Enable -1    One column output
[*]   Enable -a    Include entries which start with .
[*]   Enable -A    Like -a, but exclude . and ..
[*]   Enable -C    List by columns
[*]   Enable -x    List by lines
[*]   Enable -d    List directory entries instead of contents
[*]   Enable -L    Follow symlinks
[*]   Enable -H    Follow symlinks on command line
[*]   Enable -R    Recurse
[*]   Enable -p    Append / to dir entries
[*]   Enable -F    Append indicator (one of */=@|) to entries
[*]   Enable -l    Long listing format
[*]     Enable -c  sort by ctime
[*]     Enable -t  sort by mtime
[*]     Enable -u  sort by atime
[*]   Enable -i    List inode numbers
[*]   Enable -n    List numeric UIDs and GIDs instead of names
[*]   Enable -s    List allocated blocks
[*]   Enable -e    List full date and time
[*]   Enable -h    List sizes in human readable format (1K 243M 2G)
[*]   Enable -r    Sort in reverse order
[*]   Enable -S    Sort by size
[*]   Enable -X    Sort by extension
[*]   Enable -v    Sort by version
[*]   Enable -w N  Assume the terminal is N columns wide
[*]   Enable --color
[*]     Produce colored ls output by default

For every applet and every option. That would be ridiculous.

Ridiculous we can live with, but there is a bigger problem too.
More options means more #ifdefs and more weird interactions
between different options, making code less maintainable.
Because of this reason, some options (e.g. in top) were even
_removed_ (permanently enabled) because code was too tangled.

therefore options should be introduced if there is a reasonable
chance user actually needs to control them separately,
and if they control a nontrivial amount of code (i.e. not 20 bytes).

If user needs bash compat, it means he is not running on an extremely
constrained machine (otherwise he can well spend a bit of time and rewrite
all his scripts to be POSIX-compatible). Since the machine is not
too constrained, it's okay to just enable all of them and not worry
about having a few more kbytes of code for a bashism he doesn't need.