Avoid refreshing all hooks in secondary worktrees

This avoids "ln: failed to access '.git/hooks/foo': Not a directory"
console noise. The primary worktree's hooks are used in secondary
worktrees anyway.

Possibly using 'git rev-parse --git-dir', and putting hooks there
would be a better fix? No idea.

Change-Id: I846e065d017744e9d8dcee847d48bc1adc66d761
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/143358
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>

g

@@ -91,13 +91,16 @@ refresh_all_hooks()
     local hook
 
     pushd "${COREDIR?}" > /dev/null
-    for hook_name in "${COREDIR?}/.git-hooks"/* ; do
-        hook=".git/hooks/${hook_name##*/}"
-        if [ ! -e "${hook?}" ] || [ -L "${hook?}" ] ; then
-            rm -f "${hook?}"
-            ln -sf "${hook_name}" "${hook?}"
-        fi
-    done
+    # There's no ".git" e.g. in a secondary worktree
+    if [ -d ".git" ]; then
+        for hook_name in "${COREDIR?}/.git-hooks"/* ; do
+            hook=".git/hooks/${hook_name##*/}"
+            if [ ! -e "${hook?}" ] || [ -L "${hook?}" ] ; then
+                rm -f "${hook?}"
+                ln -sf "${hook_name}" "${hook?}"
+            fi
+        done
+    fi
 
     for repo in ${SUBMODULES_ALL?} ; do
         refresh_submodule_hooks "$repo"