Add option to specify where to look for .editorconfig files.

Adds a --config|c option which takes a directory in which the search for
.editorconfig files will start.

When --config|c is used together with explicit filenames of files to format,
.editorconfig is searched only in --config directory, and not in directories
where files are.

Fixes #240.

src/dfmt/main.d

@@ -16,7 +16,7 @@ else
     import std.stdio : stdout, stdin, stderr, writeln, File;
     import dfmt.config : Config;
     import dfmt.formatter : format;
-    import std.path : buildPath, expandTilde;
+    import std.path : buildPath, dirName, expandTilde;
     import dfmt.editorconfig : getConfigFor;
     import std.getopt : getopt, GetOptException;
 
@@ -27,6 +27,7 @@ else
         optConfig.pattern = "*.d";
         bool showHelp;
         bool showVersion;
+        string explicitConfigDir;
 
         void handleBooleans(string option, string value)
         {
@@ -68,6 +69,7 @@ else
                 "version", &showVersion,
                 "align_switch_statements", &handleBooleans,
                 "brace_style", &optConfig.dfmt_brace_style,
+                "config|c", &explicitConfigDir,
                 "end_of_line", &optConfig.end_of_line,
                 "help|h", &showHelp,
                 "indent_size", &optConfig.indent_size,
@@ -127,11 +129,31 @@ else
 
         ubyte[] buffer;
 
+        Config explicitConfig;
+        if (explicitConfigDir)
+        {
+            import std.path : exists, isDir;
+
+            if (!exists(explicitConfigDir) || !isDir(explicitConfigDir))
+            {
+                stderr.writeln("--config_dir|c must specify existing directory path");
+                return 1;
+            }
+            explicitConfig = getConfigFor!Config(explicitConfigDir);
+            explicitConfig.pattern = "*.d";
+        }
+
         if (readFromStdin)
         {
+            import std.file : getcwd;
+
             Config config;
             config.initializeWithDefaults();
-            config.merge(optConfig, null);
+            if (explicitConfigDir != "")
+            {
+                config.merge(explicitConfig, buildPath(explicitConfigDir, "dummy.d"));
+            }
+            config.merge(optConfig, buildPath(getcwd(), "dummy.d"));
             if (!config.isValid())
                 return 1;
             ubyte[4096] inputBuffer;
@@ -165,9 +187,16 @@ else
                 }
                 Config config;
                 config.initializeWithDefaults();
+                if (explicitConfigDir != "")
+                {
+                    config.merge(explicitConfig, buildPath(explicitConfigDir, "dummy.d"));
+                }
+                else
+                {
                     Config fileConfig = getConfigFor!Config(path);
                     fileConfig.pattern = "*.d";
                     config.merge(fileConfig, path);
+                }
                 config.merge(optConfig, path);
                 if (!config.isValid())
                     return 1;
@@ -207,6 +236,7 @@ https://github.com/Hackerpilot/dfmt
 Options:
     --help, -h          Print this help message
     --inplace, -i       Edit files in place
+    --config_dir, -c    Path to directory to load .editconfig file from.
     --version           Print the version number and then exit
 
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