Index: lib/Format/Format.cpp
===================================================================
--- lib/Format/Format.cpp
+++ lib/Format/Format.cpp
@@ -1963,6 +1963,8 @@
     ".clang-format file located in one of the parent\n"
     "directories of the source file (or current\n"
     "directory for stdin).\n"
+    "Use -style=file:<configfile> to explicitly specify\n"
+    "the configuration file.\n"
     "Use -style=\"{key: value, ...}\" to set specific\n"
     "parameters, e.g.:\n"
     "  -style=\"{BasedOnStyle: llvm, IndentWidth: 8}\"";
@@ -2009,6 +2011,30 @@
     return Style;
   }
 
+  // Check for explicit config filename
+  if (StyleName.startswith_lower("file:")) {
+    SmallString<128> ConfigFile(StyleName.substr(5));
+    auto Status = FS->status(ConfigFile.str());
+    bool FoundConfigFile =
+        Status && (Status->getType() == llvm::sys::fs::file_type::regular_file);
+    if (!FoundConfigFile) {
+      return make_string_error("Configuration file " + ConfigFile + " not found");
+    }
+    llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> Text =
+        FS->getBufferForFile(ConfigFile.str());
+    if (std::error_code EC = Text.getError())
+      return make_string_error(EC.message());
+    if (std::error_code ec = parseConfiguration(Text.get()->getBuffer(), &Style)) {
+      if (ec == ParseError::Unsuitable) {
+        return make_string_error("Configuration file " + ConfigFile +
+          " does not support " + getLanguageName(Style.Language));
+      }
+      return make_string_error("Error reading " + ConfigFile + ": " + ec.message());
+    }
+    DEBUG(llvm::dbgs() << "Using configuration file " << ConfigFile << "\n");
+    return Style;
+  }
+
   if (!StyleName.equals_lower("file")) {
     if (!getPredefinedStyle(StyleName, Style.Language, &Style))
       return make_string_error("Invalid value for -style");