feat: git-based nightly versions

scripts/nightly-version.sh

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+# Print an auto-generated nightly version string derived from git history:
+#
+#   <last-release-tag>+<commits-since>.g<short-sha>     e.g., 26.8.0+14.gb1a2c3d4
+#
+# When no release has been tagged yet, the base is 0.0.0 and the count is the
+# total number of commits:
+#
+#   0.0.0+<total-commits>.g<short-sha>                  e.g., 0.0.0+57.gb1a2c3d4
+#
+# The `+...` part is SemVer build metadata, so the string stays a valid version
+# and never sorts ahead of the release it is based on. Needs full history and
+# tags (check out with fetch-depth: 0 and fetch-tags: true). Release tags are
+# matched as N.N.N; the moving `nightly` tag is ignored.
+set -euo pipefail
+sha="$(git rev-parse --short=8 HEAD)"
+if desc="$(git describe --tags --long \
+            --match '[0-9]*.[0-9]*.[0-9]*' --exclude nightly 2>/dev/null)"; then
+  # desc is <tag>-<n>-g<hash>; the tag itself has no '-', so strip from the right.
+  rest="${desc%-g*}"     # <tag>-<n>
+  n="${rest##*-}"        # <n>
+  tag="${rest%-*}"       # <tag>
+  echo "${tag}+${n}.g${sha}"
+else
+  n="$(git rev-list --count HEAD)"
+  echo "0.0.0+${n}.g${sha}"
+fi