Update install functions to work with a docset name argument

These functions were extracting the content of the tar.gz file and taking the
docset name from the extracted folder. This was limiting us because, for
example, Dash has 3 different docsets for Lua (Lua_5.1, Lua_5.2, Lua_5.3) but
the folder name of all of them would be just "Lua".  With this change, we're
replicating exactly the same directory structure of Dash app for official
docsets. Ex: `.../Lua_5.1/Lua.docset/.../

helm-dash.el

@@ -277,7 +277,7 @@ Report an error unless a valid docset is selected."
   "Download a docset from URL and install with name DOCSET-NAME."
   (let ((docset-tmp-path (format "%s%s-docset.tgz" temporary-file-directory docset-name)))
     (url-copy-file url docset-tmp-path t)
-    (helm-dash-install-docset-from-file docset-tmp-path)))
+    (helm-dash-install-docset-from-file docset-name docset-tmp-path)))
 
 (defun helm-dash--ensure-created-docsets-path (docset-path)
   "Check if DOCSET-PATH directory exists.
@@ -299,20 +299,25 @@ If doesn't exist, it asks to create it."
 
 
 ;;;###autoload
-(defun helm-dash-install-docset-from-file (docset-tmp-path)
-  "Extract the content of DOCSET-TMP-PATH, move it to `helm-dash-docsets-path` and activate the docset."
+(defun helm-dash-install-docset-from-file (docset-name docset-path)
+  "Install a docset from a tar.gz file.
+For a docset with name DOCSET-NAME, extract the content of the
+file with path DOCSET-PATH, move it to
+`helm-dash-docsets-path' and activate the docset."
   (interactive
-   (list (car (find-file-read-args "Docset Tarball: " t))))
-  (let ((docset-folder
-         (helm-dash-docset-folder-name
-          (shell-command-to-string
-           (format "tar xvf %s -C %s"
-                   (shell-quote-argument (expand-file-name docset-tmp-path))
-                   (shell-quote-argument (helm-dash-docsets-path)))))))
-    (helm-dash-activate-docset docset-folder)
-    (message (format
-              "Docset installed. Add \"%s\" to helm-dash-common-docsets or helm-dash-docsets."
-              docset-folder))))
+   (list (read-string "Docset name: " nil)
+         (car (find-file-read-args "Docset Tarball: " t))))
+  (let ((docset-tar-path (expand-file-name docset-path))
+        (docset-out-path (expand-file-name docset-name (helm-dash-docsets-path))))
+    (mkdir docset-out-path)
+    (shell-command-to-string
+     (format "tar xvf %s -C %s"
+             (shell-quote-argument docset-tar-path)
+             (shell-quote-argument docset-out-path))))
+  (helm-dash-activate-docset docset-name)
+  (message (format
+            "Docset installed. Add \"%s\" to helm-dash-common-docsets or helm-dash-docsets."
+            docset-name)))
 
 ;;;###autoload
 (defun helm-dash-install-docset (docset-name)
@@ -347,37 +352,30 @@ If doesn't exist, it asks to create it."
               ;; Beware! This lambda is run in it's own instance of emacs.
               (url-file-local-copy docset-url))
             (lambda (docset-tmp-path)
-              (helm-dash-async-install-docset-from-file docset-tmp-path)))))))))
+              (helm-dash-async-install-docset-from-file docset-name docset-tmp-path)))))))))
 
 ;;;###autoload
-(defun helm-dash-async-install-docset-from-file (docset-tmp-path)
+(defun helm-dash-async-install-docset-from-file (docset-name docset-tmp-path)
   "Asynchronously extract the content of DOCSET-TMP-PATH, move it to `helm-dash-docsets-path` and activate the docset."
   (interactive (list (car (find-file-read-args "Docset Tarball: " t))))
   (let ((docset-tar-path (expand-file-name docset-tmp-path))
-        (docset-out-path (helm-dash-docsets-path)))
+        (docset-out-path (expand-file-name docset-name (helm-dash-docsets-path))))
     (async-start
      (lambda ()
        ;; Beware! This lambda is run in it's own instance of emacs.
+       (mkdir docset-out-path)
        (shell-command-to-string
         (format "tar xvf %s -C %s"
                 (shell-quote-argument docset-tar-path)
                 (shell-quote-argument docset-out-path))))
      (lambda (shell-output)
-       (let ((docset-folder (helm-dash-docset-folder-name shell-output)))
-         (helm-dash-activate-docset docset-folder)
-         (message (format
-                   "Docset installed. Add \"%s\" to helm-dash-common-docsets or helm-dash-docsets."
-                   docset-folder)))))))
+       (helm-dash-activate-docset docset-name)
+       (message (format
+                 "Docset installed. Add \"%s\" to helm-dash-common-docsets or helm-dash-docsets."
+                 docset-name))))))
 
 (defalias 'helm-dash-update-docset 'helm-dash-install-docset)
 
-(defun helm-dash-docset-folder-name (tar-output)
-  "Return the name of the folder where the docset has been extracted.
-The argument TAR-OUTPUT should be an string with the output of a tar command."
-  (let ((last-line
-         (car (last (split-string tar-output "\n" t)))))
-    (replace-regexp-in-string "^x " "" (car (split-string last-line "\\." t)))))
-
 (defun helm-dash-get-docset-url (feed-path)
   "Parse a xml feed with docset urls and return the first url.
 The Argument FEED-PATH should be a string with the path of the xml file."