Tweak shell program resolution slightly

- Path containing '/' or '\' are resolved relative to the current
   directory, rather than using the path. Paths starting with '/' still
   resolve relative to the root directory.
 - Shell completion will also include sub-directories of the current
   directory.

Closes #219

src/main/resources/assets/computercraft/lua/rom/programs/shell.lua

@@ -237,9 +237,8 @@ function shell.resolveProgram( _sCommand )
     end
 
     -- If the path is a global path, use it directly
-    local sStartChar = string.sub( _sCommand, 1, 1 )
+    if _sCommand:find("/") or _sCommand:find("\\") then
-    if sStartChar == "/" or sStartChar == "\\" then
+        local sPath = shell.resolve( _sCommand )
-        local sPath = fs.combine( "", _sCommand )
         if fs.exists( sPath ) and not fs.isDir( sPath ) then
             return sPath
         else
@@ -299,9 +298,9 @@ function shell.programs( _bIncludeHidden )
 end
 
 local function completeProgram( sLine )
-    if #sLine > 0 and string.sub( sLine, 1, 1 ) == "/" then
+    if #sLine > 0 and (sLine:find("/") or sLine:find("\\")) then
         -- Add programs from the root
-        return fs.complete( sLine, "", true, false )
+        return fs.complete( sLine, sDir, true, false )
 
     else
         local tResults = {}
@@ -318,6 +317,16 @@ local function completeProgram( sLine )
             end
         end
 
+        -- Add all subdirectories. We don't include files as they will be added in the block below
+        local tDirs = fs.complete( sLine, sDir, false, false )
+        for i = 1, #tDirs do
+            if not tSeen[ sResult ] then
+                local sResult = tDirs[i]
+                table.insert (tResults, sResult )
+                tSeen [ sResult ] = true
+            end
+        end
+
         -- Add programs from the path
         local tPrograms = shell.programs()
         for n=1,#tPrograms do