Fix absolute path in Makefile

src/FileUtils.h

@@ -6,6 +6,7 @@
 #include "Common.h"
 #include <cstring>
 #include <vector>
+#include <algorithm>
 #include <stdlib.h>
 
 struct FileUtils
@@ -23,6 +24,60 @@ struct FileUtils
     return filename;
   }
 
+  static std::string GetRelativePath(std::string from, std::string to)
+  {
+    std::string result;
+    if(to[to.size()-1] == '/')
+      to.pop_back();
+    if(from[from.size()-1] == '/')
+      from.pop_back();
+
+    // Check if the directory is inside 'from'
+    if(strncmp(to.c_str(), from.c_str(), from.size()) == 0)
+    {
+      // Same directory
+      if(to.size() == from.size())
+        return "";
+      // Remove the 'from' path
+      return to.substr(from.size()+1);
+    }
+    // Check if the directory is a child of from 
+    else if(strncmp(from.c_str(), to.c_str(), to.size()) == 0)
+    {
+      std::string sub = from.substr(to.size());
+      size_t n = std::count(sub.begin(), sub.end(), '/');
+      for(int i = 0;i<n;i++)
+      {
+        result+="..";
+        if(i != n-1)
+          result+="/";
+      }
+      return result;
+    }
+    // Otherwise it's a path in another directory
+    else
+    {
+      // Find the most common directory
+      std::string commonPath = CommonPrefix(from,to);
+      while(commonPath.back() != '/')
+        commonPath.pop_back();
+      commonPath.pop_back();
+
+      // Go back to the common directory
+      std::string sub = from.substr(commonPath.size());
+      size_t n = std::count(sub.begin(), sub.end(), '/');
+      for(int i = 0;i<n;i++)
+      {
+        result+="..";
+        if(i != n-1)
+          result+="/";
+      }
+      // Add the path which diverges
+      result += to.substr(commonPath.size());
+      return result;
+    }
+  }
+
   static void GetAllFiles(const std::string& folder, std::vector<std::string>& files)
   {
     DIR* dp;