Add uninstall directive to manifest

Allows for removal of old files or packages

steps/helpers.sh

@@ -79,9 +79,11 @@ _grep() {
 
 get_revision() {
     local pkg=$1
+    local oldpwd="${PWD}"
     cd "/external/repo"
     # Get revision (n time this package has been built)
     revision=$( (ls -1 "${pkg}"* 2>/dev/null || true) | wc -l | sed 's/ *//g')
+    cd "${oldpwd}"
 }
 
 # Installs binary packages from an earlier run
@@ -108,6 +110,64 @@ bin_preseed() {
     return 1
 }
 
+# Removes either an existing package or file
+uninstall() {
+    local in_fs in_pkg symlinks
+    while [ $# -gt 0 ]; do
+        removing="$1"
+        case "${removing}" in
+            /*)
+                # Removing a file
+                echo "removing file: ${removing}."
+                rm -f "${removing}"
+                ;;
+            *)
+                echo "${removing}: uninstalling."
+                local oldpwd="${PWD}"
+                mkdir -p "/tmp/removing"
+                cd "/tmp/removing"
+                get_revision "${removing}"
+                local filename="/external/repo/${removing}_$((revision-1)).tar.bz2"
+                # Initial bzip2 built against meslibc has broken pipes
+                bzip2 -dc "${filename}" | tar -xf -
+                # reverse to have files before directories
+                if command -v find >/dev/null 2>&1; then
+                    find . | sort -r > ../filelist
+                else
+                    get_files . | tac > ../filelist
+                fi
+                # shellcheck disable=SC2162
+                while read file; do
+                    if [ -d "${file}" ]; then
+                        if [ -z "$(ls -A "/${file}")" ]; then
+                            rmdir "/${file}"
+                        fi
+                    else
+                        # in some cases we might be uninstalling a file that has already been overwritten
+                        # in this case we don't want to remove it
+                        in_fs="$(sha256sum "${file}" 2>/dev/null | cut -d' ' -f1)"
+                        in_pkg="$(sha256sum "/${file}" 2>/dev/null | cut -d' ' -f1)"
+                        if [ "${in_fs}" = "${in_pkg}" ]; then
+                            rm -f "/${file}"
+                        fi
+                        if [ -h "${file}" ]; then
+                            symlinks="${symlinks} ${file}"
+                        fi
+                    fi
+                done < ../filelist
+                rm -f ../filelist
+                for link in ${symlinks}; do
+                    if [ ! -e "/${link}" ]; then
+                        rm -f "/${link}"
+                    fi
+                done
+                cd "${oldpwd}"
+                ;;
+        esac
+        shift
+    done
+}
+
 # Common build steps
 # Build function provides a few common stages with default implementation
 # that can be overridden on per package basis in the build script.
@@ -236,6 +296,7 @@ extract_file() {
         *)
             case "${f}" in
                 *.tar* | *.tgz)
+                    # shellcheck disable=SC2153
                     if test -e "${PREFIX}/libexec/rmt"; then
                         # Again, we want to split out into words.
                         # shellcheck disable=SC2086

steps/manifest

@@ -15,6 +15,9 @@
 #   eg, define: BUILD_FIWIX = KERNEL_BOOTSTRAP == True || BUILD_KERNELS == True
 # - jump: jump (usually) to a new kernel, executes a script with that name
 #   eg, jump: fiwix
+# - uninstall; removes a package or filenames
+#   eg, uninstall: perl-5.6.2
+#   eg, uninstall: /usr/bin/lex /usr/bin/flex
 #
 # The following directives have special significance:
 # - build directives beginning with "bash" (as well as jumps) trigger the generation of