create-new-feature.sh --json can fail with '10#Fetching: value too great for base'

[ignatremizov]

Summary

Running scripts/bash/create-new-feature.sh --json can fail with:

line 250: 10#Fetching: value too great for base (error token is "10#Fetching")

Reproduction

1. In any git repo, run:

bash /path/to/spec-kit/scripts/bash/create-new-feature.sh --json "Native-like month/year scrolling selector mode"

2. Observe failure:

.../create-new-feature.sh: line 250: 10#Fetching: value too great for base (error token is "10#Fetching")

Script location

• scripts/bash/create-new-feature.sh
• Failing line: FEATURE_NUM=$(printf "%03d" "$((10#$BRANCH_NUMBER))")

Likely cause

BRANCH_NUMBER is populated via command substitution:

BRANCH_NUMBER=$(check_existing_branches "$SPECS_DIR")

Inside check_existing_branches, this runs:

git fetch --all --prune 2>/dev/null || true

If git fetch --all writes status text like Fetching ... to stdout, command substitution captures that output along with the numeric result, so BRANCH_NUMBER can become a non-numeric string (for example Fetching...), which then breaks numeric expansion on line 250.

Suggested fix

Silence both stdout and stderr for fetch (or otherwise ensure check_existing_branches emits only the final integer):

git fetch --all --prune >/dev/null 2>&1 || true

Environment

• Date observed: 2026-02-11
• Invocation target repo: /Users/iremizov/code/vue-tailwind-datepicker
• Script source repo: github/spec-kit