release: better support for binary Debian package

This commit beefs up the package metadata used by the 'cargo deb' tool to
produce a binary dpkg. In particular, we now include ripgrep's man page.

This commit includes a new script, 'ci/build_deb.sh', which will handle
the build process for a dpkg, which has become a bit more nuanced than
just running 'cargo deb'. We don't (yet) run this script in CI.

Fixes #842

ci/build_deb.sh

@@ -0,0 +1,31 @@
+#!/bin/bash
+
+set -e
+
+# This script builds a binary dpkg for Debian based distros. It does not
+# currently run in CI, and is instead run manually and the resulting dpkg is
+# uploaded to GitHub via the web UI.
+#
+# Note that this requires 'cargo deb', which can be installed with
+# 'cargo install cargo-deb'.
+#
+# This should be run from the root of the ripgrep repo.
+
+if ! command -V cargo-deb > /dev/null 2>&1; then
+    echo "cargo-deb command missing" >&2
+    exit 1
+fi
+
+# 'cargo deb' does not seem to provide a way to specify an asset that is
+# created at build time, such as ripgrep's man page. To work around this,
+# we force a debug build, copy out the man page produced from that build, put
+# it into a predictable location and then build the deb, which knows where to
+# look.
+
+mkdir -p deployment
+cargo build
+manpage="$(find ./target/debug -name rg.1 -print0 | xargs -0 ls -t | head -n1)"
+cp "$manpage" deployment/
+# Since we're distributing the dpkg, we don't know whether the user will have
+# PCRE2 installed, so just do a static build.
+PCRE2_SYS_STATIC=1 cargo deb