changelog file is optional in bump script

scripts/bump

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 
 # developed on macOS and probably doesn't work on Linux yet due to minor
 # differences in flags on sed
@@ -21,12 +21,9 @@ README_FILE=$DIR/README.md
 
 # determine changelog file name
 if [ -f "$DIR/CHANGES.md" ]; then
-    CHANGELOG_FILE=$DIR/CHANGES.md
+    CHANGELOG_FILE="$DIR/CHANGES.md"
 elif [ -f "$DIR/CHANGELOG.md" ]; then
-    CHANGELOG_FILE=$DIR/CHANGELOG.md
-else
-    echo "No changelog file found"
-    exit 1
+    CHANGELOG_FILE="$DIR/CHANGELOG.md"
 fi
 
 # get current version
@@ -37,15 +34,17 @@ CHANGE_CHUNK_FILE="$(mktemp)"
 echo saving changelog to $CHANGE_CHUNK_FILE
 echo
 
-# get changelog chunk and save to temp file
-cat "$CHANGELOG_FILE" |
-    # skip up to unreleased heading
-    sed '1,/Unreleased/ d' |
-    # take up to previous version heading
-    sed "/$CURRENT_VERSION/ q" |
-    # drop last line
-    sed '$d' \
-        >"$CHANGE_CHUNK_FILE"
+if [ -n "${CHANGELOG_FILE-}" ]; then
+    # get changelog chunk and save to temp file
+    cat "$CHANGELOG_FILE" |
+        # skip up to unreleased heading
+        sed '1,/Unreleased/ d' |
+        # take up to previous version heading
+        sed "/$CURRENT_VERSION/ q" |
+        # drop last line
+        sed '$d' \
+            >"$CHANGE_CHUNK_FILE"
+fi
 
 # if word count of changelog chunk is 0 then insert filler changelog chunk
 if [ "$(wc -w "$CHANGE_CHUNK_FILE" | awk '{ print $1 }')" = "0" ]; then
@@ -68,28 +67,29 @@ if [ "${NEW_VERSION:0:1}" = "v" ]; then
     NEW_VERSION="${NEW_VERSION:1}"
 fi
 
-DATE="$(date -u +"%Y-%m-%d")"
-echo "updating from $CURRENT_VERSION => $NEW_VERSION ($DATE)"
+echo "updating from $CURRENT_VERSION => $NEW_VERSION"
 
 # update package.version field
 sed -i.bak -E "s/^version ?= ?\"[^\"]+\"$/version = \"$NEW_VERSION\"/" "$CARGO_MANIFEST"
 
 # update readme
 [ -f "$README_FILE" ] && sed -i.bak -E "s#$CURRENT_VERSION([/)])#$NEW_VERSION\1#g" "$README_FILE"
 
-# update changelog file
-(
-    sed '/Unreleased/ q' "$CHANGELOG_FILE"                   # up to unreleased heading
-    echo                                                     # blank line
-    echo "## $NEW_VERSION - $DATE"                           # new version heading
-    cat "$CHANGE_CHUNK_FILE"                                 # previously unreleased changes
-    sed "/$CURRENT_VERSION/ q" "$CHANGELOG_FILE" | tail -n 1 # the previous version heading
-    sed "1,/$CURRENT_VERSION/ d" "$CHANGELOG_FILE"           # everything after previous version heading
-) >"$CHANGELOG_FILE.bak"
-mv "$CHANGELOG_FILE.bak" "$CHANGELOG_FILE"
-
-# format CHANGELOG file according to prettier
-npx -y prettier --write "$CHANGELOG_FILE" || true
+if [ -n "${CHANGELOG_FILE-}" ]; then
+    # update changelog file
+    (
+        sed '/Unreleased/ q' "$CHANGELOG_FILE"                   # up to unreleased heading
+        echo                                                     # blank line
+        echo "## $NEW_VERSION"                                   # new version heading
+        cat "$CHANGE_CHUNK_FILE"                                 # previously unreleased changes
+        sed "/$CURRENT_VERSION/ q" "$CHANGELOG_FILE" | tail -n 1 # the previous version heading
+        sed "1,/$CURRENT_VERSION/ d" "$CHANGELOG_FILE"           # everything after previous version heading
+    ) >"$CHANGELOG_FILE.bak"
+    mv "$CHANGELOG_FILE.bak" "$CHANGELOG_FILE"
+
+    # format CHANGELOG file according to prettier
+    npx -y prettier --write "$CHANGELOG_FILE" || true
+fi
 
 # done; remove backup files
 rm -f $CARGO_MANIFEST.bak