TT#76658 Use temp file to prepare ngcpcfg_perms file

Two parallel ngcpcfg processes corrupts this file as they try to write
into it simultaneously.

As a solution use temporary file to prepare the content of ngcpcfg_perms
file and then move it to /etc/ngcp-config/.ngcpcfg_perms.

Change-Id: I74baf3ac78a80d96a1b9dfba2be063b7128b1150

hooks/pre-commit

@@ -99,13 +99,15 @@ generate_metadata() {
   '
 }
 
-echo "# Generated by ngcpcfg. Do not edit." > .ngcpcfg_perms
-echo >> .ngcpcfg_perms
-
+ngcpcfg_perms=$(mktemp)
+chown root:root "${ngcpcfg_perms}"
 # Make sure the file is not readable by others, since it can leak
 # information about contents of non-readable directories
-chmod 700 .ngcpcfg_perms
+chmod 700 "${ngcpcfg_perms}"
 
-generate_metadata >> .ngcpcfg_perms
+echo "# Generated by ngcpcfg. Do not edit." > "${ngcpcfg_perms}"
+echo >> "${ngcpcfg_perms}"
+generate_metadata >> "${ngcpcfg_perms}"
+mv "${ngcpcfg_perms}" .ngcpcfg_perms
 
 git add .ngcpcfg_perms