update docs + tests for xapian-delve use

Since -cindex uses the xapian-delve(1) command for `--prune'
functionality, we'll rename our `xapian-compact' dependency to
the Debian package name (xapian-tools) since `xapian-delve' is
in the same package.

1 files changed, 3 insertions, 2 deletions

diff --git a/INSTALL b/INSTALL
index 2e1c7ef7..617801cc 100644
--- a/INSTALL
+++ b/INSTALL
@@ -111,10 +111,11 @@ Numerous optional modules are likely to be useful as well:
 * highlight                        deb: libhighlight-perl
                                    (for syntax highlighting with coderepo)
 
-* xapian-compact (tool)            deb: xapian-tools
+* xapian-tools                     deb: xapian-tools
                                    pkg: xapian-core
                                    rpm: xapian-core
-                                   (only for public-inbox-compact(1))
+                                   (for public-inbox-compact(1) and
+                                    public-inbox-cindex(1))
 
 * curl (tool)                      deb, pkg, rpm: curl
                                    (for HTTP(S) externals with curl)