List pub cache location: `pub cache show`

[DartBot]

Originally opened as dart-lang/sdk#20652

This issue was originally filed by guillermo.l...@gmail.com

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Hi,

At least on Windows, it's hard to see where the cache is located. Could we have an option to list the pub cache location(s)?

Regards,
Guillermo

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2108507?v=3" align="left" width="48" height="48"hspace="10"> Comment by dgrove

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Added Area-Pub, Triaged labels.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/188?v=3" align="left" width="48" height="48"hspace="10"> Comment by nex3

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It always defaults to $APPDATA/Pub/Cache on Windows. I don't think it's worth adding a command to print this out.

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Added NotPlanned label.

[gspencergoog]

The cache can also be placed in a location pointed to by the PUB_CACHE env var, so it would be good to be able to print out the actual path that pub is planning to use. This would help Flutter in that we wouldn't need to duplicate the cache location selection logic (sure, not complicated, but still) before calling pub in order to print out the one we think it is using.

[jmagman]

This would have helped us when the default location changed on Windows: #2297.