Add isReadable, isWritable, isExecutable utilities (#376)

Fixes #354

Author: sake92

Readme.adoc

@@ -1555,6 +1555,51 @@ os.isLink(wd / "misc/folder-symlink") ==> true
 os.isLink(wd / "folder1") ==> false
 ----
 
+==== `os.isReadable`
+
+[source,scala]
+----
+os.isReadable(p: Path): Boolean
+----
+
+Returns `true` if the given path is readable.
+
+[source,scala]
+----
+os.isReadable(wd / "misc/file1") ==> false
+os.isReadable(wd / "misc/file2") ==> true
+----
+
+==== `os.isWritable`
+
+[source,scala]
+----
+os.isWritable(p: Path): Boolean
+----
+
+Returns `true` if the given path is writable.
+
+[source,scala]
+----
+os.isWritable(wd / "misc/file1") ==> false
+os.isWritable(wd / "misc/file2") ==> true
+----
+
+==== `os.isExecutable`
+
+[source,scala]
+----
+os.isExecutable(p: Path): Boolean
+----
+
+Returns `true` if the given path is executable.
+
+[source,scala]
+----
+os.isExecutable(wd / "misc/file1") ==> false
+os.isExecutable(wd / "misc/file2.sh") ==> true
+----
+
 ==== `os.size`
 
 [source,scala]

os/src/StatOps.scala

@@ -40,6 +40,33 @@ object isDir extends Function1[Path, Boolean] {
   }
 }
 
+/**
+ * Checks whether the given path is readable
+ *
+ * Returns `false` if the path does not exist
+ */
+object isReadable extends Function1[Path, Boolean] {
+  def apply(p: Path): Boolean = Files.isReadable(p.wrapped)
+}
+
+/**
+ * Checks whether the given path is writable
+ *
+ * Returns `false` if the path does not exist
+ */
+object isWritable extends Function1[Path, Boolean] {
+  def apply(p: Path): Boolean = Files.isWritable(p.wrapped)
+}
+
+/**
+ * Checks whether the given path is executable
+ *
+ * Returns `false` if the path does not exist
+ */
+object isExecutable extends Function1[Path, Boolean] {
+  def apply(p: Path): Boolean = Files.isExecutable(p.wrapped)
+}
+
 /**
  * Gets the size of the given file or folder
  *

os/test/src/FilesystemMetadataTests.scala

@@ -50,6 +50,27 @@ object FilesystemMetadataTests extends TestSuite {
         os.isLink(wd / "folder1") ==> false
       }
     }
+    test("isReadable") {
+      test - prep { wd =>
+        os.isReadable(wd / "File.txt") ==> true
+        os.isReadable(wd / "folder1") ==> true
+      }
+    }
+    test("isWritable") {
+      test - prep { wd =>
+        os.isWritable(wd / "File.txt") ==> true
+        os.isWritable(wd / "folder1") ==> true
+      }
+    }
+    test("isExecutable") {
+      test - prep { wd =>
+        if (Unix()) {
+          os.perms.set(wd / "File.txt", "rw-rw-rw-")
+          os.isExecutable(wd / "File.txt") ==> false
+          os.isExecutable(wd / "misc/echo") ==> true
+        }
+      }
+    }
     test("size") {
       test - prep { wd =>
         os.size(wd / "File.txt") ==> 8