Add VIM built-in package management to readme (#1049)

* Save/Set screen state also on WinLeave and WinEnter.

The particular use case here is when switching tabs with `gt` and the
NERDTrees have been mirrored.

* Update version number and change log.

.github/PULL_REQUEST_TEMPLATE.md

@@ -5,9 +5,12 @@ Closes #  <!-- Issue number this PR addresses. If none, remove this line. -->
 ---
 ### New Version Info
 
-- [ ] Derive a new version number. Increment the:
+#### Author's Instructions
-    - [ ] `MAJOR` version when you make incompatible API changes
+- [ ] Derive a new `MAJOR.MINOR.PATCH` version number. Increment the:
-    - [ ] `MINOR` version when you add functionality in a backwards-compatible manner
+    - `MAJOR` version when you make incompatible API changes
-    - [ ] `PATCH` version when you make backwards-compatible bug fixes
+    - `MINOR` version when you add functionality in a backwards-compatible manner
+    - `PATCH` version when you make backwards-compatible bug fixes
 - [ ] Update [CHANGELOG.md](https://github.com/scrooloose/nerdtree/blob/master/CHANGELOG.md), following the established pattern.
-- [ ] Tag the merge commit, e.g. `git tag -a 3.1.4 -m "v3.1.4" && git push origin --tags`
+#### Collaborator's Instructions
+- [ ] Review [CHANGELOG.md](https://github.com/scrooloose/nerdtree/blob/master/CHANGELOG.md), suggesting a different version number if necessary.
+- [ ] After merge, tag the merge commit, e.g. `git tag -a 3.1.4 -m "v3.1.4" && git push origin --tags`

CHANGELOG.md

@@ -1,16 +1,28 @@
-# Change Log
+# NERDTree Change Log
 
-#### 6.1...
+<!--
+    Introduce a new MAJOR.MINOR version with a 4-hash header.
+
+    PATCH versions are listed from newest to oldest under their respective MAJOR.MINOR version
+    in an unordered list.  The format is:
+        - **.PATCH**: Pull Request Title (PR Author) [PR Number](Link to PR)
+-->
+
+#### 6.1
+- **.4**: Add VIM built-in package management to read me file. (pesarkhobeee) [#1049](https://github.com/scrooloose/nerdtree/pull/1049)
+- **.3**: Save/Set screen state also on WinLeave and WinEnter. (PhilRunninger) [#1048](https://github.com/scrooloose/nerdtree/pull/1048)
+- **.2**: Wrap saveScreenState's statements in a try-catch block. (PhilRunninger) [#1047](https://github.com/scrooloose/nerdtree/pull/1047)
+- **.1**: Catch errors when trying to read CHANGELOG.md. (PhilRunninger) [#1045](https://github.com/scrooloose/nerdtree/pull/1045)
 - **.0**: If file path doesn't exist, :NERDTreeFind its parent directory instead. (PhilRunninger) [#1043](https://github.com/scrooloose/nerdtree/pull/1043)
-#### 6.0...
+#### 6.0
 - **.1**: Reintroduce necessary variable mistakenly removed. (PhilRunninger) [#1040](https://github.com/scrooloose/nerdtree/pull/1040)
 - **.0**: Make the behavior of window splits consistent (dragonxlwang, PhilRunninger) [#1035](https://github.com/scrooloose/nerdtree/pull/1035)
-#### 5.3...
+#### 5.3
 - **.3**: Fix (p)ath not displaying in the minimal menu (tuzz) [#1038](https://github.com/scrooloose/nerdtree/pull/1038)
 - **.2**: Enable events when closing NerdTree window. (PhilRunninger) [#1037](https://github.com/scrooloose/nerdtree/pull/1037)
 - **.1**: Fix the `e` key mapping to use netrw if desired (PhilRunninger) [#1031](https://github.com/scrooloose/nerdtree/pull/1031)
 - **.0**: Add file extension and size to sorting capabilities (PhilRunninger) [#1029](https://github.com/scrooloose/nerdtree/pull/1029)
-#### 5.2...
+#### 5.2
 - **.9**: Suppress events for intermediate window/tab/buffer changes (PhilRunninger) [#1026](https://github.com/scrooloose/nerdtree/pull/1026)
 - **.8**: Revert [#1019](https://github.com/scrooloose/nerdtree/pull/1019) to fix nvim artifacts and flickering. (PhilRunninger) [#1021](https://github.com/scrooloose/nerdtree/pull/1021)
 - **.7**: Use :mode only in neovim. MacVim still needs to use :redraw! (PhilRunninger) [#1019](https://github.com/scrooloose/nerdtree/pull/1019)
@@ -21,7 +33,7 @@
 - **.2**: Make Enter work on the `.. ( up a dir )` line (PhilRunninger) [#1013](https://github.com/scrooloose/nerdtree/pull/1013)
 - **.1**: Fix nerdtree#version() on Windows. (PhilRunninger)
 - **.0**: Expand functionality of `<CR>` mapping. (PhilRunninger) [#1011](https://github.com/scrooloose/nerdtree/pull/1011)
-#### 5.1...
+#### 5.1
 - **.3**: Remove @mentions from PR template and change log. They weren't working. (PhilRunninger) [#1009](https://github.com/scrooloose/nerdtree/pull/1009)
 - **.2**: Fix NERDTree opening with the wrong size. (PhilRunninger) [#1008](https://github.com/scrooloose/nerdtree/pull/1008)
 - **.1**: Update Changelog and create PR Template (PhilRunninger) [#1007](https://github.com/scrooloose/nerdtree/pull/1007)

README.markdown

@@ -17,6 +17,13 @@ included documentation.
 Installation
 ------------
 
+If you are using VIM version 8 or higher you can use its built-in package management; see `:help packages` for more information. Just run these commands in your terminal:
+
+    git clone https://github.com/scrooloose/nerdtree.git ~/.vim/pack/vendor/start/nerdtree
+    vim -u NONE -c "helptags ~/.vim/pack/vendor/start/nerdtree/doc" -c q
+
+Otherwise, these are some of the other options:
+
 #### [pathogen.vim](https://github.com/tpope/vim-pathogen)
 
     git clone https://github.com/scrooloose/nerdtree.git ~/.vim/bundle/nerdtree

autoload/nerdtree.vim

@@ -10,8 +10,9 @@ let s:rootNERDTreePath = resolve(expand("<sfile>:p:h:h"))
 "  change log is shown for the current version; otherwise, only the version
 "  number is shown.
 function! nerdtree#version(...)
-    let l:changelog = readfile(join([s:rootNERDTreePath, "CHANGELOG.md"], nerdtree#slash()))
     let l:text = 'Unknown'
+    try
+        let l:changelog = readfile(join([s:rootNERDTreePath, "CHANGELOG.md"], nerdtree#slash()))
         let l:line = 0
         while l:line <= len(l:changelog)
             if l:changelog[l:line] =~ '\d\+\.\d\+'
@@ -21,6 +22,8 @@ function! nerdtree#version(...)
             endif
             let l:line += 1
         endwhile
+    catch
+    endtry
     return l:text
 endfunction
 

lib/nerdtree/ui.vim

@@ -355,12 +355,15 @@ endfunction
 " scroll position
 function! s:UI.saveScreenState()
     let win = winnr()
-    call g:NERDTree.CursorToTreeWin()
     let self._screenState = {}
+    try
+        call g:NERDTree.CursorToTreeWin()
         let self._screenState['oldPos'] = getpos(".")
         let self._screenState['oldTopLine'] = line("w0")
         let self._screenState['oldWindowSize']= winwidth("")
         call nerdtree#exec(win . "wincmd w", 1)
+    catch
+    endtry
 endfunction
 
 " FUNCTION: s:UI.setShowHidden(val) {{{1

plugin/NERD_tree.vim

@@ -170,10 +170,10 @@ call nerdtree#ui_glue#setupCommands()
 "============================================================
 augroup NERDTree
     "Save the cursor position whenever we close the nerd tree
-    exec "autocmd BufLeave ". g:NERDTreeCreator.BufNamePrefix() ."* if g:NERDTree.IsOpen() | call b:NERDTree.ui.saveScreenState() | endif"
+    exec "autocmd BufLeave,WinLeave ". g:NERDTreeCreator.BufNamePrefix() ."* if g:NERDTree.IsOpen() | call b:NERDTree.ui.saveScreenState() | endif"
 
     "disallow insert mode in the NERDTree
-    exec "autocmd BufEnter ". g:NERDTreeCreator.BufNamePrefix() ."* stopinsert"
+    exec "autocmd BufEnter,WinEnter ". g:NERDTreeCreator.BufNamePrefix() ."* stopinsert"
 augroup END
 
 if g:NERDTreeHijackNetrw