Make fs.combine accept multiple arguments

Means we can now do fs.combine("a", "b", "c"). Of course, one may just
write "a/b/c" in this case, but it's definitely useful elsewhere.

This is /technically/ a breaking change as fs.combine(a, b:gsub(...))
will no longer function (as gsub returns multiple arguments). However,
I've done a quick search through GH and my Pastebin archives and can't
find any programs which would break. Fingers crossed.

patchwork.md

@@ -374,3 +374,17 @@ or numbers.
 
 Fixes #591
 ```
+
+```
+d4199064ae5ae8023c589f80f12d94e1c6bbc2b5
+
+Make fs.combine accept multiple arguments
+
+Means we can now do fs.combine("a", "b", "c"). Of course, one may just
+write "a/b/c" in this case, but it's definitely useful elsewhere.
+
+This is /technically/ a breaking change as fs.combine(a, b:gsub(...))
+will no longer function (as gsub returns multiple arguments). However,
+I've done a quick search through GH and my Pastebin archives and can't
+find any programs which would break. Fingers crossed.
+```

src/main/java/dan200/computercraft/core/apis/FSAPI.java

@@ -17,6 +17,8 @@ import java.util.Map;
 import java.util.OptionalLong;
 import java.util.function.Function;
 
+
+import dan200.computercraft.api.lua.IArguments;
 import dan200.computercraft.api.lua.ILuaAPI;
 import dan200.computercraft.api.lua.LuaException;
 import dan200.computercraft.api.lua.LuaFunction;
@@ -75,15 +77,27 @@ public class FSAPI implements ILuaAPI {
     }
 
     /**
-     * Combines two parts of a path into one full path, adding separators as needed.
+     * Combines several parts of a path into one full path, adding separators as
+     * needed
      *
-     * @param pathA The first part of the path. For example, a parent directory path.
+     * @param arguments The paths to combine.
-     * @param pathB The second part of the path. For example, a file name.
      * @return The new path, with separators added between parts as needed.
+     * @cc.tparam string path The first part of the path. For example, a parent directory path.
+     * @cc.tparam string ... Additional parts of the path to combine.
+     * @throws LuaException On argument errors.
      */
     @LuaFunction
-    public final String combine(String pathA, String pathB) {
+    public final String combine( IArguments arguments ) throws LuaException {
-        return this.fileSystem.combine(pathA, pathB);
+        StringBuilder result = new StringBuilder();
+        result.append(FileSystem.sanitizePath(arguments.getString(0), true));
+
+        for (int i = 1, n = arguments.count(); i < n; i++) {
+            String part = FileSystem.sanitizePath(arguments.getString(i), true);
+            if (result.length() != 0 && !part.isEmpty()) result.append('/');
+            result.append(part);
+        }
+
+        return FileSystem.sanitizePath(result.toString(), true);
     }
 
     /**

src/main/java/dan200/computercraft/core/filesystem/FileSystem.java

@@ -76,7 +76,7 @@ public class FileSystem {
         this.mounts.put(location, wrapper);
     }
 
-    private static String sanitizePath(String path, boolean allowWildcards) {
+    public static String sanitizePath(String path, boolean allowWildcards) {
         // Allow windowsy slashes
         path = path.replace('\\', '/');
 
@@ -231,7 +231,7 @@ public class FileSystem {
         this.mounts.remove(sanitizePath(path));
     }
 
-    public synchronized String combine(String path, String childPath) {
+    public String combine( String path, String childPath ) {
         path = sanitizePath(path, true);
         childPath = sanitizePath(childPath, true);