doc export: regex support

Allows for command like this:
`drive pull -export doc`
Equal to
`drive pull -export docx`
and any other similar formats bunched together

README.md

@@ -59,17 +59,27 @@ Background sync is not just hard, it's stupid. My technical and philosophical ra
 exported to different forms e.g docx, xlsx, csv etc.
 When doing a pull remember to include option `-export ext1,ext2,ext3`
 where ext1, ext2, ... could be:
-    * docx
-    * jpeg
+    * doc, docx
+    * jpeg, jpg
+    * gif
     * html
     * odt
     * rtf
     * pdf
     * png
-    * pptx
+    * ppt, pptx
     * svg
-    * txt
-    * xlsx
+    * txt, text
+    * xls, xlsx
+
+The exported files will be placed in a directory in the same path
+as the source Doc but affixed with '\_exports' e.g
+drive pull -export gif,jpg,svg logo
+if successful will create a directory logo\_exports which will look like:
+|- logo\_exports
+                |- logo.gif
+                |- logo.png
+                |- logo.svg
 
 ## Known issues
 * Probably, it doesn't work on Windows.

pull.go

@@ -153,10 +153,7 @@ func (g *Commands) export(f *File, destAbsPath string, exports []string) (manife
 
 	waitables := map[string]string{}
 	for _, ext := range exports {
-		mimeType, ok = docExportsMap[ext]
-		if !ok {
-			continue
-		}
+		mimeType = mimeTypeFromExt(ext)
 		exportURL, ok = f.ExportLinks[mimeType]
 		if !ok {
 			continue

remote.go

@@ -19,6 +19,7 @@ import (
 	"fmt"
 	"io"
 	"net/http"
+	"regexp"
 	"strings"
 	"time"
 
@@ -46,25 +47,46 @@ var (
 	ErrPathNotExists = errors.New("remote path doesn't exist")
 )
 
-var docExportsMap = map[string]string{
-	"csv":  "text/csv",
-	"html": "text/html",
-	"txt":  "text/plain",
+var regExtStrMap = map[string]string{
+	"csv":   "text/csv",
+	"html?": "text/html",
+	"te?xt": "text/plain",
 
-	"gif":  "image/gif",
-	"png":  "image/png",
-	"svg":  "image/svg+xml",
-	"jpeg": "image/jpeg",
+	"gif":   "image/gif",
+	"png":   "image/png",
+	"svg":   "image/svg+xml",
+	"jpe?g": "image/jpeg",
 
 	"odt": "application/vnd.oasis.opendocument.text",
 	"rtf": "application/rtf",
 	"pdf": "application/pdf",
 
-	"docx": "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
-	"pptx": "application/vnd.openxmlformats-officedocument.wordprocessingml.presentation",
+	"docx?": "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
+	"pptx?": "application/vnd.openxmlformats-officedocument.wordprocessingml.presentation",
+	"xlsx?": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
+}
+
+func compileRegExtMap() *map[*regexp.Regexp]string {
+	regExpMap := make(map[*regexp.Regexp]string)
+	for regStr, mimeType := range regExtStrMap {
+		regExComp, err := regexp.Compile(regStr)
+		if err == nil {
+			regExpMap[regExComp] = mimeType
+		}
+	}
+	return &regExpMap
+}
+
+var regExtMap = *compileRegExtMap()
 
-	"xls":  "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
-	"xlsx": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
+func mimeTypeFromExt(ext string) string {
+	bExt := []byte(ext)
+	for regEx, mimeType := range regExtMap {
+		if regEx != nil && regEx.Match(bExt) {
+			return mimeType
+		}
+	}
+	return ""
 }
 
 type Remote struct {