feat(cli): add --quiet / -q option (#281)

* feat(cli): add --quiet / -q option

Stops any successful output. Errors are still outputted.

* refactor(cli): create output functions

This commit creates stdout and stderr functions for outputting with
respect to isQuiet and adds support for differing (easier to parse)
messages if not connected to a TTY (eg. a pipe or process substitution)

Additionally changes the 'No matching files.' message to output on stderr
rather than on stdout as it was, which makes sense because this output
represents erroneous usage.

* fix(cli): ensure --quiet isn't used as a pattern

--help and --version don't need to be checked because they
exit the program before reaching this point.

* fix(cli): add --quiet to the help

* fix(cli): change stderr to not respect --quiet

* fix(cli): change stdout to stderr in isTerminal

* refactor(cli): simplify output functions

* refactor(cli): remove call to array.filter

* test: add tests for version, help, and quiet

README.md

@@ -69,6 +69,15 @@ $ sort-package-json "**/package.json" --check
 # 2 of 5 matched files are not sorted.
 ```
 
+#### `--quiet` flag
+
+In order to silence any successful output, you can run CLI with the `--quiet` flag (or `-q`). This will stop the CLI from outputting if it runs successfully, but will still display errors if they occur. Exit codes will not change.
+
+```bash
+$ sort-package-json "**/package.json" --check --quiet
+$ sort-package-json "**/package.json" --quiet
+```
+
 ## API
 
 ### Install

cli.js

@@ -7,9 +7,15 @@ const isCheckFlag = (argument) => argument === '--check' || argument === '-c'
 const isHelpFlag = (argument) => argument === '--help' || argument === '-h'
 const isVersionFlag = (argument) =>
   argument === '--version' || argument === '-v'
+const isQuietFlag = (argument) => argument === '--quiet' || argument === '-q'
 
 const cliArguments = process.argv.slice(2)
 const isCheck = cliArguments.some(isCheckFlag)
+const isQuiet = cliArguments.some(isQuietFlag)
+
+const stdout = isQuiet ? () => {} : console.log
+const stderr = console.error
+
 const isHelp = cliArguments.some(isHelpFlag)
 const isVersion = cliArguments.some(isVersionFlag)
 
@@ -20,6 +26,7 @@ Sort npm package.json files. Default: ./package.json
 Strings passed as files are parsed as globs.
 
   -c, --check                check if FILES are sorted
+  -q, --quiet                don't output success messages
   -h, --help                 display this help and exit
   -v, --version              display the version and exit
   `,
@@ -35,7 +42,9 @@ if (isVersion) {
   process.exit(0)
 }
 
-const patterns = cliArguments.filter((argument) => !isCheckFlag(argument))
+const patterns = cliArguments.filter(
+  (argument) => !isCheckFlag(argument) && !isQuietFlag(argument),
+)
 
 if (!patterns.length) {
   patterns[0] = 'package.json'
@@ -44,7 +53,7 @@ if (!patterns.length) {
 const files = globbySync(patterns)
 
 if (files.length === 0) {
-  console.log('No matching files.')
+  stderr('No matching files.')
   process.exit(1)
 }
 
@@ -57,24 +66,24 @@ files.forEach((file) => {
   if (sorted !== packageJson) {
     if (isCheck) {
       notSortedFiles++
-      console.log(file)
+      stdout(file)
     } else {
       fs.writeFileSync(file, sorted, 'utf8')
-      console.log(`${file} is sorted!`)
+      stdout(`${file} is sorted!`)
     }
   }
 })
 
 if (isCheck) {
-  console.log()
+  stdout()
   if (notSortedFiles) {
-    console.log(
+    stdout(
       notSortedFiles === 1
         ? `${notSortedFiles} of ${files.length} matched file is not sorted.`
         : `${notSortedFiles} of ${files.length} matched files are not sorted.`,
     )
   } else {
-    console.log(
+    stdout(
       files.length === 1
         ? `${files.length} matched file is sorted.`
         : `${files.length} matched files are sorted.`,