fix: no IPFS_JS_EXEC during 1st pass of test-external

[lidel]

Parent issue: ipfs/js-ipfs#2706

This fix ensures IPFS_JS_EXEC is ignored during the first run of npm test in test-external.
It will work as expected during the second time npm test is run.

Motivation

We want to run ipfs-webui tests in ipfs/js-ipfs#2706,
however, for some reason E2E tests do not use the ipfs from file:*.tgz defined in package.json.

I am not sure what is happening exactly, connect-deps does not do the trick, only setting IPFS_JS_EXEC works. Either way, this seems to be a useful fix to merge anyway, as it removes potential side effect from initial pass.

cc @hugomrdias

[achingbrain]

LGTM but presumably we want to leave the rest of the env intact?

E.g instead do:

env: {
  ...process.env,
  // ensure custom js-ipfs is not used for the first run
  IPFS_JS_EXEC: undefined
}

[lidel]

@achingbrain the rest of env is left intact, execa (lib used for exec) extends by default:

https://www.npmjs.com/package/execa#env:

env

Type: object
Default: process.env

Environment key-value pairs. Extends automatically from process.env.
Set extendEnv to false if you don't want this.

[lidel]

@hugomrdias do you mind merging and releasing, so we can unblock ipfs/js-ipfs#2706?
(I believe fix for the connect-deps issue could land separately, but if you want me to wait for it, its fine too)

[hugomrdias]

the main reason for this change was the webui tests and that was fixed with ipfsd-ctl v1.0.6.
i prefer to not mess with env without a clear reason, so im closing this without merging. In the future if we find another reason to do this ill merge this change.

thank you all for helping.