docs: document --parents flag for files.write command (#349)

Also adds a test.

Already supported in `js-ipfs`, `go-ipfs` requires ipfs/kubo#5359
to be merged and released

SPEC/FILES.md

@@ -880,6 +880,7 @@ Where:
   - `offset` is an Integer with the byte offset to begin writing at (default: 0)
   - `create` is a Boolean to indicate to create the file if it doesn't exist (default: false)
   - `truncate` is a Boolean to indicate if the file should be truncated after writing all the bytes from `content` (default: false)
+  - `parents` is a Boolean value to decide whether or not to make the parent directories if they don't exist (default: false)
   - `length` is an Integer with the maximum number of bytes to read (default: Read all bytes from `content`)
   - `raw-leaves`: if true, DAG leaves will contain raw file data and not be wrapped in a protobuf (boolean, default false)
   - `cid-version`: the CID version to use when storing the data (storage keys are based on the CID, including it's version) (integer, default 0)

js/src/files/write.js

@@ -40,12 +40,31 @@ module.exports = (createCommon, options) => {
       })
     })
 
-    it('should write to non existent file with create flag, expect no error', function (done) {
-      const testDir = `/test-${hat()}`
+    it('should write to non existent file with create flag', function (done) {
+      const testPath = `/test-${hat()}`
 
-      ipfs.files.write(testDir, Buffer.from('Hello, world!'), {create: true}, (err) => {
+      ipfs.files.write(testPath, Buffer.from('Hello, world!'), {create: true}, (err) => {
         expect(err).to.not.exist()
-        done()
+
+        ipfs.files.stat(testPath, (err, stats) => {
+          expect(err).to.not.exist()
+          expect(stats.type).to.equal('file')
+          done()
+        })
+      })
+    })
+
+    it('should write to deeply nested non existent file with create and parents flags', function (done) {
+      const testPath = `/foo/bar/baz/test-${hat()}`
+
+      ipfs.files.write(testPath, Buffer.from('Hello, world!'), {create: true, parents: true}, (err) => {
+        expect(err).to.not.exist()
+
+        ipfs.files.stat(testPath, (err, stats) => {
+          expect(err).to.not.exist()
+          expect(stats.type).to.equal('file')
+          done()
+        })
       })
     })
   })