x/tools/cmd/goimports: provide a flag for the local import path prefix

[kr]

My company has tried to adopt a convention placing import paths into three groups: standard library followed by third-party packages followed by local packages. For example

import (
    "database/sql"
    "io"
    "strconv"

    "github.com/lib/pq"

    "mycompany.com/foo/bar"
    "mycompany.com/foo/baz"
)

We'd like to be able to add a flag to our goimports-on-save hook, like

goimports -local mycompany.com/

to tell goimports to put any paths beginning with "mycompany.com/" into our third group. I think that would end up as group value 3 in the goimports source: stdlib=0, 3rd party=1, appengine=2, then local=3.

If this sounds reasonable, I can write a patch.

[ianlancetaylor]

CC @bradfitz

[bradfitz]

Seems fine I guess. I suppose to tell your editor to pass the argument you might need to make a wrapper program which added the arg, depending on your editor.

[kr]

I just sent https://golang.org/cl/25145.

If matchPattern were handy, I would have made this a pattern like 'example.com/...'. But a simple prefix gets the job done (for me anyway).

The plumbing was a little gross. I'm all ears for a cleaner approach.

[gopherbot]

CL https://golang.org/cl/25145 mentions this issue.