cmd/cue/cmd: make import path specification more shell friendly

[cueckoo]

Originally opened by @cHolzberger in cuelang/cue#176

the restructuring with -l is not working on windows with the given examples

cue import -l '"\(name)"' test.yaml 

with a test.yaml of

name: test
value: whatever

always results in

parser error in path "\\(name)": illegal character U+005C '\'

i think this should be working as the documentation states U+005C as the right character to start string-interpolation. tried on last release.

[cueckoo]

Original reply by @mpvl in cuelang/cue#176 (comment)

It looks like the double quotes are dropped by your shell as well (the double quotes in the error message are added by CUE). I don't know how escaping works in PowerShell so I don't know how to solve this. Could you try using a different shell?

[cueckoo]

Original reply by @mpvl in cuelang/cue#176 (comment)

Looking at the PowerShell docs, it uses back tick for escaping and the usual bash quoting indeed won't work for escaping. You will have to adjust the examples to work with PowerShell or use a different shell.
IIUC

cue import -l `"\(name)`" test.yaml 

should work, but I have no means of testing this.

[cueckoo]

Original reply by @mpvl in cuelang/cue#176 (comment)

With the new syntax (using colons rather than spaces), the current specification of -l is a bit awkward. It makes sense to change the syntax at some point. I'll see if a syntax that doesn't need quoting as much makes sense. This could make examples work on both shells, at least, although incompatibilities will inevitably remain.