ioc: don't prune pre-selected directories.

When pruning modules, some of them might contain special cases where it
is harder to automatically detect in the pruning algorithm. While users
could workaround this by specifying such special paths under APP_DIRS,
this can be handled here by adding extra tooling to be used by modules.

Introduce a way for modules to specify extra paths that must be kept,
besides those detected by lnls-prune-artifacts. Do this through a
.lnls-keep-paths file that specifies all relative paths (directories or
files) whose contents must be kept. Paths may be globs, so that they are
resolved based on their bash expansion, avoiding hard-coded options when
ambiguity can be automatically resolved.

These exceptions are considered for all ancestors of a candidate to
removal, so that they are not restricted to EPICS modules themselves.
This eases implementation because we won't need to detect which parent
is a module and should contain .lnls-keep-paths, and instead simply
traverse the whole ancestor list looking if any of them defines one.

base/lnls-prune-artifacts.sh

@@ -77,13 +77,42 @@ get_used_epics_modules() {
     filter_out_paths "$all_modules" "$unused_modules"
 }
 
+# Traverse ancestor directories of each provided path, and concatenate all
+# their .lnls-keep-paths defined entries as absolute paths.
+get_defined_paths_to_keep() {
+    for path; do
+        if [ "${path:0:1}" != "/" ]; then
+            >&2 echo "error: get_defined_paths_to_keep() expects absolute paths, but got '$path'"
+            exit 1
+        fi
+
+        while true; do
+            keep_path_file="$path/.lnls-keep-paths"
+
+            if [ -f "$keep_path_file" ]; then
+                keep_paths=$(cat "$keep_path_file")
+
+                for keep_path in $keep_paths; do
+                    # output it as an absolute path
+                    realpath "$path"/$keep_path
+                done
+            fi
+
+            [ "$path" == "/" ] && break
+
+            path=$(dirname $path)
+        done
+    done | sort -u
+}
+
 prune_module_dirs() {
     module=$1
 
     module_dirs=$(find $module -type d)
     keep_paths=$(cat << EOF
 $(find_shared_libraries $module)
 $(find $module -type f -regex ".*\.\(cmd\|db\|template\|req\|substitutions\)" -printf "%h\n" | sort -u)
+$(get_defined_paths_to_keep $module)
 EOF
     )
 
@@ -154,11 +183,16 @@ remove_unused_shared_libraries() {
         remove_libs=$(echo "$remove_libs" | grep -vx $lib)
     done
 
+    keep_paths=$(get_defined_paths_to_keep $remove_libs)
+
     for lib in $remove_libs; do
-        size=$(du -hs $lib | cut -f 1)
+        # if library is not found inside any $keep_dirs, remove it
+        if find $keep_paths -path "$lib" -exec false {} +; then
+            size=$(du -hs $lib | cut -f 1)
 
-        echo "Removing shared library '$lib' ($size)"
-        rm -f ${lib%.so*}.so*
+            echo "Removing shared library '$lib' ($size)"
+            rm -f ${lib%.so*}.so*
+        fi
     done
 }