Add support for relative path option

[bgalletbgallet]

Add the possibility to use --relative=true option in command line
This is useful if you run your test on a linux environment (docker, vm, server) and dev on a windows one.
If you want your coverage to work with your IDE, you need relative path instead of absolute ones.

Linked with pull request istanbuljs/istanbuljs#492

[coreyfarrell]

Suggested change

	relative: this.config.relative === 'true',
	projectRoot: this.cwd,

[bgalletbgallet]

Hi @coreyfarrell
Shouldn't I use this.config.cwd to access the cwd option ?

[coreyfarrell]

No, please use this.cwd. In some edge cases it's possible that this.config.cwd might be unset but this.cwd has the default process.cwd().

https://github.com/istanbuljs/nyc/blob/master/index.js#L60

[bgalletbgallet]

Perfect I didn't see it was already set. I do it tonight
Thank you for your anwser

[coreyfarrell]

I've altered the suggested change per my latest comment on the istanbuljs PR.

[bgalletbgallet]

@coreyfarrell Everything should be ok, the issue with --cwd option is still present but this PR is not concerned anymore.
By default the lcov report is relative. A customer projectRoot option can be used to change the 'from' argument of the path.relative() function

[coreyfarrell]

@bcoe This adds a projectRoot option to nyc which could be set differently than cwd. Do you think this is useful? I'm concerned this could cause confusion for users.

Ref #1234 - the config loading is complicated and potentially needs some tweaks before we do a final release of nyc 15.

[bcoe]

@coreyfarrell this would be extremely useful to me, I'm currently floating a patch for the Node.js nightly builds, with almost this functionality (so that merging works):

https://codecov.io/gh/nodejs/node/src/64ee64d3afc837350ee39058cef9179e92f3554c/lib/fs.js

[coreyfarrell]

@bgalletbgallet could you explain to me why we need a separate option for projectRoot compared to cwd? I'm very concerned this will cause confusion to end users, and interested in knowing about a scenario where the value of cwd will would be unacceptable as the base of reporting. Keep in mind that by default cwd will be the directory containing the package.json which applies to process.cwd(). I'm afraid to add complexity without understanding the justification.

A minimal reproduction which installs git://github.com/bgalletbgallet/nyc#master for the nyc dependency showing that it is necessary to set projectRoot to get functional results would be great.

[bgalletbgallet]

@coreyfarrell I don't know, I was about to delete it and @bcoe told that it was usefull to him. I don't see any case where you need a different projectRoot than the default cwd. If it's ok for @bcoe, we will delete it

[coreyfarrell]

I believe @bcoe was mixed up with the reviews, he's actually using the istanbul-lib-report / istanbul-reports modules directly in c8.

As for nyc I would still like to have projectRoot: this.cwd passed to the reporter options. If someone has a need for projectRoot to be different from this.cwd I can consider that as a separate non-breaking change, but I'd prefer to avoid it.

[coreyfarrell]

Thanks for the contribution and for making the updates!