Store the crawl version in the textdatabases in SAVEDIR and
upgrade the databases when the crawl version changes.

By default crawl checks for a mtime difference on files in DATADIR to see if an
upgrade is required, but guix nulls all file dates,
and crawl would never upgrade saves.

diff -ur a/source/database.cc b/source/database.cc
--- a/crawl-ref/source/database.cc	2018-08-09 21:49:26.000000000 -0400
+++ b/crawl-ref/source/database.cc	2018-10-07 18:06:41.022445789 -0400
@@ -24,6 +24,7 @@
 #include "stringutil.h"
 #include "syscalls.h"
 #include "unicode.h"
+#include "version.h"
 
 // TextDB handles dependency checking the db vs text files, creating the
 // db, loading, and destroying the DB.
@@ -54,6 +55,7 @@
     vector<string> _input_files;
     DBM* _db;
     string timestamp;
+    string version;
     TextDB *_parent;
     const char* lang() { return _parent ? Options.lang_name : 0; }
 public:
@@ -163,7 +165,7 @@
 
 TextDB::TextDB(const char* db_name, const char* dir, vector<string> files)
     : _db_name(db_name), _directory(dir), _input_files(files),
-      _db(nullptr), timestamp(""), _parent(0), translation(0)
+      _db(nullptr), timestamp(""), version(""),  _parent(0), translation(0)
 {
 }
 
@@ -171,7 +173,7 @@
     : _db_name(parent->_db_name),
       _directory(parent->_directory + Options.lang_name + "/"),
       _input_files(parent->_input_files), // FIXME: pointless copy
-      _db(nullptr), timestamp(""), _parent(parent), translation(nullptr)
+      _db(nullptr), timestamp(""), version(""), _parent(parent), translation(nullptr)
 {
 }
 
@@ -186,6 +188,9 @@
         return false;
 
     timestamp = _query_database(*this, "TIMESTAMP", false, false, true);
+    version = _query_database(*this, "VERSION", false, false, true);
+    if (version.empty())
+        return false;
     if (timestamp.empty())
         return false;
 
@@ -229,6 +234,9 @@
     string ts;
     bool no_files = true;
 
+    if (string(Version::Long) != version)
+        return true;
+
     for (const string &file : _input_files)
     {
         string full_input_path = _directory + file;
@@ -246,7 +254,7 @@
         ts += buf;
     }
 
-    if (no_files)
+    if (no_files && version.empty())
     {
         // No point in empty databases, although for simplicity keep ones
         // for disappeared translations for now.
@@ -312,7 +320,10 @@
             _store_text_db(full_input_path, _db);
         }
     }
+
+    string current_version = string(Version::Long);
     _add_entry(_db, "TIMESTAMP", ts);
+    _add_entry(_db, "VERSION", current_version);
 
     dbm_close(_db);
     _db = 0;
8:30:35 -0400'>2020-05-20</span></td><td><a href='/guix/commit/tests/file-systems.scm?id=b460ba7992a0b4af2ddb5927dcf062784539ef7b'>bootloader: grub: Allow booting from a Btrfs subvolume.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/bootloader/grub.scm (strip-mount-point): Remove procedure.
(normalize-file): Add procedure.
(grub-configuration-file): New BTRFS-SUBVOLUME-FILE-NAME parameter.  When
defined, prepend its value to the kernel and initrd file names, using the
NORMALIZE-FILE procedure.  Adjust the call to EYE-CANDY to pass the
BTRFS-SUBVOLUME-FILE-NAME argument.  Normalize the KEYMAP file as well.
(eye-candy): Add a BTRFS-SUBVOLUME-FILE-NAME parameter, and use it, along with
the NORMALIZE-FILE procedure, to normalize the FONT-FILE and IMAGE nested
variables.  Adjust doc.
* gnu/bootloader/depthcharge.scm (depthcharge-configuration-file): Adapt.
* gnu/bootloader/extlinux.scm (extlinux-configuration-file): Likewise.
* gnu/system/file-systems.scm (btrfs-subvolume?)
(btrfs-store-subvolume-file-name): New procedures.
* gnu/system.scm (operating-system-bootcfg): Specify the Btrfs
subvolume file name the store resides on to the
`operating-system-bootcfg' procedure, using the new
BTRFS-SUBVOLUME-FILE-NAME argument.
* doc/guix.texi (File Systems): Add a Btrfs subsection to document the use of
subvolumes.
* gnu/tests/install.scm (%btrfs-root-on-subvolume-os)
(%btrfs-root-on-subvolume-os-source)
(%btrfs-root-on-subvolume-installation-script)
(%test-btrfs-root-on-subvolume-os): New variables.
</span></span></td><td>Maxim Cournoyer</td></tr>
<tr><td><span title='2020-05-20 08:30:34 -0400'>2020-05-20</span></td><td><a href='/guix/commit/tests/file-systems.scm?id=fa35fb58c84d1c1741e4e63c0b37074e35ed2a61'>file-systems: Add helpers for parsing the options string into an alist.</a><span class='msg-avail'>...<span class='msg-tooltip'>* gnu/system/file-systems.scm (file-system-options-&gt;alist)
(alist-&gt;file-system-options): New procedures.
* tests/file-systems.scm: New tests.
* doc/guix.texi (File Systems): Add note about the newly added procedures.
</span></span></td><td>Maxim Cournoyer</td></tr>