• closes Unable to look up source error #147

If the application is instrumented inside a Docker container, all paths have different prefix. For example, local paths could be

root/
  app/
    src/
      main.js

But when you run app in Docker container the coverage will be in some local path, so that file main.js will produce in .nyc_output/out.json file

{
  "/var/www/site/main.js": {
    "path": "/var/www/site/main.js"
  }
}

Then local Cypress running outside the container tries to generate the report - and produces an empty report, since there is no file "/var/www/site/main.js"

In this PR, if ALL files are missing, we try to find common prefix in paths, such that IF this prefix is replaced with process.cwd() then all files are found.

So if you run in /root/app, then before generating the report, this plugin will say: "Ohh, if I replace /var/www/site with /root/app/src then main.js is found!" And if the same prefix works for all files, then it updates the prefix and generates the reports.

Note: it could check the hash as well to make sure the files are exactly what we expect to find.