Fixed #613: Add option for indent on &s

doc/vimtex.txt

@@ -586,6 +586,13 @@ Options~
 
   Default value: ['document']
 
+*g:vimtex_indent_on_ampersands*
+  By default, vimtex will align on ampersands e.g. in math aligned
+  environments or in tabular environments. If this feature is not wanted it
+  may be disabled through this option.
+
+  Default value: 1
+
 *g:vimtex_index_hide_line_numbers*
   If enabled, then line numbers will be hidden in the index windows.  That is,
   |nonumber| and |norelativenumber| will be set locally.
@@ -1763,6 +1770,7 @@ Associated settings:
     |g:vimtex_indent_enabled|
     |g:vimtex_indent_bib_enabled|
     |g:vimtex_indent_ignored_envs|
+    |g:vimtex_indent_on_ampersands|
 
 ==============================================================================
 SYNTAX HIGHLIGHTING                                             *vimtex-syntax*

indent/tex.vim

@@ -38,7 +38,8 @@ function! VimtexIndent(lnum) " {{{1
   endif
 
   " Align on ampersands
-  if l:line =~# '^\s*&' && l:prev_line =~# '\\\@<!&.*'
+  if get(g:, 'vimtex_indent_on_ampersands', 1)
+        \ && l:line =~# '^\s*&' && l:prev_line =~# '\\\@<!&.*'
     return indent(a:lnum) + match(l:prev_line, '\\\@<!&') - stridx(l:line, '&')
   endif
 

test/vader/indentation.vader

@@ -244,6 +244,34 @@ Expect tex (Verify):
     \end{aligned}
   \end{equation}
 
+Given:
+Execute (let g:vimtex_indent_on_ampersands = 0):
+  let g:vimtex_indent_on_ampersands = 0
+
+Given tex (Indent: ampersands 2):
+  \begin{equation}
+      \begin{aligned}
+          1 &
+          & 2 \\
+          3 &
+          & 4 \\
+      \end{aligned}
+  \end{equation}
+
+
+Do (Indent):
+  gg=G
+
+Expect tex (Verify):
+  \begin{equation}
+    \begin{aligned}
+      1 &
+      & 2 \\
+      3 &
+      & 4 \\
+    \end{aligned}
+  \end{equation}
+
 Given tex (Indent: ignored environments):
   \documentclass{minimal}
   \usepackage{amsmath}
@@ -273,4 +301,5 @@ Expect tex (Verify):
 Given:
 Execute (unlet g:vimtex_indent_ignored_envs):
   unlet g:vimtex_indent_ignored_envs
+  unlet g:vimtex_indent_on_ampersands