deb: add completions

This commit adds Bash, zsh and fish completions to the Debian binary
package.

Fixes #1032

Cargo.toml

@@ -91,9 +91,13 @@ assets = [
   ["FAQ.md", "usr/share/doc/ripgrep/FAQ", "644"],
   # The man page is automatically generated by ripgrep's build process, so
   # this file isn't actually commited. Instead, to create a dpkg, either
-  # create a deployment directory and copy the man page to it, or use the
+  # create a deployment/deb directory and copy the man page to it, or use the
   # 'ci/build_deb.sh' script.
-  ["deployment/rg.1", "usr/share/man/man1/rg.1", "644"],
+  ["deployment/deb/rg.1", "usr/share/man/man1/rg.1", "644"],
+  # Similarly for shell completions.
+  ["deployment/deb/rg.bash", "usr/share/bash-completion/completions/rg", "644"],
+  ["deployment/deb/rg.fish", "usr/share/fish/completions/rg.fish", "644"],
+  ["deployment/deb/_rg", "usr/share/zsh/vendor-completions/", "644"],
 ]
 extended-description = """\
 ripgrep (rg) recursively searches your current directory for a regex pattern.

ci/build_deb.sh

@@ -18,14 +18,26 @@ 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.
+# we force a debug build, copy out the man page (and shell completions)
+# produced from that build, put it into a predictable location and then build
+# the deb, which knows where to look.
 
-mkdir -p deployment
+DEPLOY_DIR=deployment/deb
+mkdir -p "$DEPLOY_DIR"
 cargo build
+
+# Find and copy man page.
 manpage="$(find ./target/debug -name rg.1 -print0 | xargs -0 ls -t | head -n1)"
-cp "$manpage" deployment/
+cp "$manpage" "$DEPLOY_DIR/"
+
+# Do the same for shell completions.
+compbash="$(find ./target/debug -name rg.bash -print0 | xargs -0 ls -t | head -n1)"
+cp "$compbash" "$DEPLOY_DIR/"
+compfish="$(find ./target/debug -name rg.fish -print0 | xargs -0 ls -t | head -n1)"
+cp "$compfish" "$DEPLOY_DIR/"
+compzsh="complete/_rg"
+cp "$compzsh" "$DEPLOY_DIR/"
+
 # 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