Add autoindentation in makefile.kak, based on PR #582 by lenormf

Closes #582

rc/base/makefile.kak

@@ -5,7 +5,7 @@ hook global BufSetOption mimetype=text/x-makefile %{
     set buffer filetype makefile
 }
 
-hook global BufCreate [mM]akefile %{
+hook global BufCreate .*/?[mM]akefile %{
     set buffer filetype makefile
 }
 
@@ -23,13 +23,35 @@ addhl -group /makefile/content regex ^[\w.%]+\h*:\s 0:identifier
 addhl -group /makefile/content regex \b(ifeq|ifneq|else|endif)\b 0:keyword
 addhl -group /makefile/content regex [+?:]= 0:operator
 
+# Commands
+# ‾‾‾‾‾‾‾‾
+
+def -hidden _makefile-indent-on-new-line %{
+    eval -draft -itersel %{
+        # preserve previous line indent
+        try %{ exec -draft \;K<a-&> }
+        ## If the line above is a target indent with a tab
+        try %{ exec -draft Z k<a-x> <a-k>^[^:]+:\s<ret> z i<tab> }
+        # cleanup trailing white space son previous line
+        try %{ exec -draft k<a-x> s \h+$ <ret>d }
+        # indent after ifeq, ifneq, else
+        try %{ exec -draft Z k<a-x> <a-k> ^\h*(ifeq|ifneq|else)\b<ret> z <a-gt> }
+    }
+}
+
 # Initialization
 # ‾‾‾‾‾‾‾‾‾‾‾‾‾‾
 
 hook global WinSetOption filetype=makefile %{
     addhl ref makefile
 
+    hook window InsertChar \n -group makefile-indent _makefile-indent-on-new-line
+
     set window comment_selection_chars ""
     set window comment_line_chars "#"
 }
-hook global WinSetOption filetype=(?!makefile).* %{ rmhl makefile }
+
+hook global WinSetOption filetype=(?!makefile).* %{
+    rmhl makefile
+    rmhooks window makefile-indent
+}