Improve performance of git and mercurial prompt

This implements custom logic to detect if we're inside of working tree
and skips os calls if not. This will improve performance of prompt
handling, especially for mercurial prompt.

config/cmder.lua

@@ -2,6 +2,65 @@ function lambda_prompt_filter()
     clink.prompt.value = string.gsub(clink.prompt.value, "{lamb}", "λ")
 end
 
+---
+ -- Resolves closest directory location for specified directory.
+ -- Navigates subsequently up one level and tries to find specified directory
+ -- @param  {string} path    Path to directory will be checked. If not provided
+ --                          current directory will be used
+ -- @param  {string} dirname Directory name to search for
+ -- @return {string} Path to specified directory or nil if such dir not found
+local function get_dir_contains(path, dirname)
+
+    -- return parent path for specified entry (either file or directory)
+    local function pathname(path)
+        local prefix = ""
+        local i = path:find("[\\/:][^\\/:]*$")
+        if i then
+            prefix = path:sub(1, i-1)
+        end
+        return prefix
+    end
+
+    -- Navigates up one level
+    local function up_one_level(path)
+        if path == nil then path = '.' end
+        if path == '.' then path = clink.get_cwd() end
+        return pathname(path)
+    end
+
+    -- Checks if provided directory contains git directory
+    local function has_specified_dir(path, specified_dir)
+        if path == nil then path = '.' end
+        local found_dirs = clink.find_dirs(path..'/'..specified_dir)
+        if #found_dirs > 0 then return true end
+        return false
+    end
+
+    -- Set default path to current directory
+    if path == nil then path = '.' end
+
+    -- If we're already have .git directory here, then return current path
+    if has_specified_dir(path, dirname) then
+        return path..'/'..dirname
+    else
+        -- Otherwise go up one level and make a recursive call
+        local parent_path = up_one_level(path)
+        if parent_path == path then
+            return nil
+        else
+            return get_dir_contains(parent_path, dirname)
+        end
+    end
+end
+
+local function get_hg_dir(path)
+    return get_dir_contains(path, '.hg')
+end
+
+local function get_git_dir(path)
+    return get_dir_contains(path, '.git')
+end
+
 ---
  -- Find out current branch
  -- @return {false|mercurial branch name}
@@ -36,18 +95,20 @@ function hg_prompt_filter()
         dirty = "\x1b[31;1m",
     }
 
-    local branch = get_hg_branch()
+    if get_hg_dir() then
-    if branch then
+        -- if we're inside of mercurial repo then try to detect current branch
-        -- Has branch => therefore it is a mercurial folder, now figure out status
+        local branch = get_hg_branch()
-        if get_hg_status() then
+        if branch then
-            color = colors.clean
+            -- Has branch => therefore it is a mercurial folder, now figure out status
-        else
+            if get_hg_status() then
-            color = colors.dirty
+                color = colors.clean
-        end
+            else
+                color = colors.dirty
+            end
 
-        clink.prompt.value = string.gsub(clink.prompt.value, "{hg}", color.."("..branch..")")
+            clink.prompt.value = string.gsub(clink.prompt.value, "{hg}", color.."("..branch..")")
-        clink.prompt.value = string.gsub(clink.prompt.value, "{git}", "")
+            return false
-        return true
+        end
     end
 
     -- No mercurial present or not in mercurial file
@@ -86,18 +147,20 @@ function git_prompt_filter()
         dirty = "\x1b[31;1m",
     }
 
-    local branch = get_git_branch()
+    if get_git_dir() then
-    if branch then
+        -- if we're inside of git repo then try to detect current branch
-        -- Has branch => therefore it is a git folder, now figure out status
+        local branch = get_git_branch()
-        if get_git_status() then
+        if branch then
-            color = colors.clean
+            -- Has branch => therefore it is a git folder, now figure out status
-        else
+            if get_git_status() then
-            color = colors.dirty
+                color = colors.clean
-        end
+            else
+                color = colors.dirty
+            end
 
-        clink.prompt.value = string.gsub(clink.prompt.value, "{git}", color.."("..branch..")")
+            clink.prompt.value = string.gsub(clink.prompt.value, "{git}", color.."("..branch..")")
-        clink.prompt.value = string.gsub(clink.prompt.value, "{hg}", "")
+            return false
-        return true
+        end
     end
 
     -- No git present or not in git file