Hi,

Can we add support for PKGBUILD(1) files for Emacs which are used to
install packages from AUR(Arch User Repository).

PKGBUILD are just normal shell script files, so we just have to add
sh mode to it:
diff --git a/lisp/files.el b/lisp/files.el
index 68e883513c..7d01938144 100644
--- a/lisp/files.el
+++ b/lisp/files.el
@@ -2723,6 +2723,7 @@ auto-mode-alist
      ("\\.scm\\.[0-9]*\\'" . scheme-mode)
      ("\\.[ckz]?sh\\'\\|\\.shar\\'\\|/\\.z?profile\\'" . sh-mode)
      ("\\.bash\\'" . sh-mode)
+     ("PKGBUILD$" . sh-mode)
      ("\\(/\\|\\`\\)\\.\\(bash_\\(profile\\|history\\|log\\(in\\|out\\)\\)\\|z?log\\(in\\|out\\)\\)\\'" . sh-mode)
      ("\\(/\\|\\`\\)\\.\\(shrc\\|zshrc\\|m?kshrc\\|bashrc\\|t?cshrc\\|esrc\\)\\'" . sh-mode)
      ("\\(/\\|\\`\\)\\.\\([kz]shenv\\|xinitrc\\|startxrc\\|xsession\\)\\'" . sh-mode)

There is also a special pkgbuild-mode(2) for editing these files which
is also an derivation of sh-mode.

[1]: https://wiki.archlinux.org/index.php/PKGBUILD
[2]: https://github.com/juergenhoetzel/pkgbuild-mode
-- 
Utkarsh Singh