Fixed #559: Strange indentation due to ampersands

indent/tex.vim

@@ -44,7 +44,7 @@ function! VimtexIndent(lnum) " {{{1
     return indent(a:lnum)
   endif
 
-  let l:nprev = s:get_prev_line(l:nprev, 'ignore-ampersands')
+  let l:nprev = s:get_prev_line(l:nprev)
   if l:nprev == 0 | return 0 | endif
   let l:prev = getline(l:nprev)
 
@@ -56,16 +56,12 @@ function! VimtexIndent(lnum) " {{{1
 endfunction
 "}}}
 
-function! s:get_prev_line(lnum, ...) " {{{1
-  let l:ignore_amps = a:0 > 0
-
+function! s:get_prev_line(lnum) " {{{1
   let l:lnum = a:lnum
   let l:prev = getline(l:lnum)
 
   while l:lnum != 0
-        \ && (l:prev =~# '^\s*%'
-          \ || s:is_verbatim(l:prev, l:lnum)
-          \ || match(l:prev, '\\\@<!&') >= 0)
+        \ && (l:prev =~# '^\s*%' || s:is_verbatim(l:prev, l:lnum))
     let l:lnum = prevnonblank(l:lnum - 1)
     let l:prev = getline(l:lnum)
   endwhile

test/vader/indentation.vader

@@ -172,3 +172,44 @@ Expect tex (Verify):
       not affect verbatim environments!
   \end{lstlisting}
 
+Given tex (Indent: With ampersands):
+  \begin{tabular}{cc}
+      \begin{tabular}{c}
+          Cell 1
+      \end{tabular} &
+      \begin{tabular}{c}
+          Cell 2
+      \end{tabular}
+  \end{tabular}
+
+  \begin{equation}
+      \begin{aligned}
+          & \left(
+          \begin{bmatrix}
+              123
+          \end{bmatrix} \right)
+      \end{aligned}
+  \end{equation}
+
+Do (Indent):
+  gg=G
+
+Expect tex (Verify):
+  \begin{tabular}{cc}
+    \begin{tabular}{c}
+      Cell 1
+    \end{tabular} &
+    \begin{tabular}{c}
+      Cell 2
+    \end{tabular}
+  \end{tabular}
+
+  \begin{equation}
+    \begin{aligned}
+      & \left(
+        \begin{bmatrix}
+          123
+      \end{bmatrix} \right)
+    \end{aligned}
+  \end{equation}
+