I want to move a file from a directory different from the current directory. This is the solution I thought of:
mv (cd ~/Downloads; ls -t | head -1 | xargs -I {} readlink -f {}) ./
There is probably a better way, but along the way I found that my expectation of the change of directory staying inside the subcommand was wrong: Running cd changes the directory where mv is being executed.
So, is there a way to change directories only for the current subcommand, without affecting the top command?
Right, many of us coming from Posix shells like bash or zsh are used to being able to run a command substitution like this using $() or just backticks and leave the parent shell environment untouched. It's a nice trick, IMHO.
On the other hand, fish doesn't automatically create a subshell when using its command substitution operator (). There's a feature request here for that, but the workaround (as suggested there) is fairly straightforward -- Just explicitly create a subshell inside the command substitution. E.g.:
mv (fish -c 'cd ~/Downloads; ls -t | head -1 | xargs -I {} readlink -f {}') ./
The downside is that syntax highlighting/checking doesn't work in the quoted text, and quoting/escaping rules get more complicated.