update-repos: simplify looping through directories

Signed-off-by: Mattia Rizzolo <mapreri@ubuntu.com>

update-repos.sh

 #!/bin/bash
 # Copyright (c) 2018 Pietro Albini <pietroalbini@ubuntu-it.org>
+#               2018 Mattia Rizzolo <mapreri@ubuntu.com>
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files (the "Software"), to deal
@@ -20,19 +21,17 @@
 # SOFTWARE.
 
 set -euo pipefail
-IFS=$'\n\t'
 
 REPOS_DIR="repos"
 
-repos="$(ls "${REPOS_DIR}")"
-for repo in $repos; do
+for repo in "$REPOS_DIR"/*; do
     # Update the repo
-    git -C "${REPOS_DIR}/${repo}" fetch --all
-    git -C "${REPOS_DIR}/${repo}" reset --hard origin/master
+    git -C "${repo}" fetch --all
+    git -C "${repo}" reset --hard origin/master
 
     # Commit the changes
-    git add "${REPOS_DIR}/${repo}"
+    git add "${repo}"
     if ! git diff --staged --exit-code --quiet; then
-        git commit -m "${REPOS_DIR}/${repo}: use latest commit"
+        git commit -m "${repo}: use latest commit"
     fi
 done