Set nyc color watermarks based on check-coverage levels

I got tired of doing --100, and then everything still looking green, making
it harder to find the test that's short on coverage.

Anything below the desired level is red.  Green starts halfway between the
desired level and 100%.

bin/run.js

@@ -251,15 +251,28 @@ const nycReporter = options =>
 const runNyc = (cmd, programArgs, options, spawnOpts) => {
   const reporter = nycReporter(options)
 
+  const branches = Math.max(+options.branches || 100, 100)
+  const lines = Math.max(+options.lines || 100, 100)
+  const functions = Math.max(+options.functions || 100, 100)
+  const statements = Math.max(+options.statements || 100, 100)
+
   const args = [
     nycBin,
     ...cmd,
     ...(options['show-process-tree'] ? ['--show-process-tree'] : []),
     '--cache=true',
-    '--branches=' + options.branches,
+    '--branches=' + branches,
+    '--watermarks.branches=' + branches,
+    '--watermarks.branches=' + (branches + (100 - branches)/2),
     '--functions=' + options.functions,
+    '--watermarks.functions=' + functions,
+    '--watermarks.functions=' + (functions + (100 - functions)/2),
     '--lines=' + options.lines,
+    '--watermarks.lines=' + lines,
+    '--watermarks.lines=' + (lines + (100 - lines)/2),
     '--statements=' + options.statements,
+    '--watermarks.statements=' + statements,
+    '--watermarks.statements=' + (statements + (100 - statements)/2),
     ...reporter,
     '--extension=.js',
     '--extension=.jsx',

tap-snapshots/test-run-coverage.js-TAP.test.js

@@ -54,6 +54,16 @@ All files | 75 | 75 | 100 | 75 | |
 
 `
 
+exports[`test/run/coverage.js TAP in 100 mode, <100 is red, not yellow > text output and 100 check 1`] = `
+-|-|-|-|-|-|
+File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Lines |
+-|-|-|-|-|-|
+All files |       75 |       75 |      100 |       75 |                   |
+ ok.js    |       75 |       75 |      100 |       75 |                 6 |
+-|-|-|-|-|-|
+
+`
+
 exports[`test/run/coverage.js TAP pipe to service > human output 1`] = `
 -|-|-|-|-|-|
 File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Lines |

test/run/coverage.js

@@ -103,6 +103,14 @@ t.test('report with checks', t => {
   })
 })
 
+t.test('in 100 mode, <100 is red, not yellow', t => {
+  escape(['--100', '--coverage-report=text', '--color'], null, (er, o, e) => {
+    t.match(er, { code: 1 })
+    t.matchSnapshot(o, 'text output and 100 check', { skip: winSkip })
+    t.end()
+  })
+})
+
 t.test('pipe to service', t => {
   const piper = tmpfile(t, 'piper.js', `
     process.stdin.pipe(process.stderr)