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/source/database.cc	2018-08-09 21:49:26.000000000 -0400
+++ b/source/database.cc	2018-10-07 18:06:41.022445789 -0400
@@ -25,6 +25,7 @@
 #include "syscalls.h"
 #include "threads.h"
 #include "unicode.h"
+#include "version.h"
 
 // TextDB handles dependency checking the db vs text files, creating the
 // db, loading, and destroying the DB.
@@ -55,6 +56,7 @@
     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;
@@ -245,7 +253,7 @@
         ts += buf;
     }
 
-    if (no_files && timestamp.empty())
+    if (no_files && timestamp.empty() && version.empty())
     {
         // No point in empty databases, although for simplicity keep ones
         // for disappeared translations for now.
@@ -313,7 +321,10 @@
             _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;
aea9eb301cfddbc4c82ddb'>tests: opam: Test additional syntax.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2020-10-02 00:30:23 +0200'>2020-10-02</span></td><td><a href='/guix/commit/tests/opam.scm?id=ad05537e32173403d034a0d552092f566abd05a5'>tests: opam: Factorize tests.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2020-01-17 14:22:07 +0100'>2020-01-17</span></td><td><a href='/guix/commit/tests/opam.scm?id=282f91790a5bbd0d9b3223c4bfd45b66e418c200'>import: opam: Avoid uses of '@@' in tests.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-09-07 22:25:14 +0200'>2019-09-07</span></td><td><a href='/guix/commit/tests/opam.scm?id=1d03a9198db6f3656a34d62eb89e5f7d5a99e76a'>tests: opam: Fix input type in import test.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2019-02-05 22:33:06 +0100'>2019-02-05</span></td><td><a href='/guix/commit/tests/opam.scm?id=0f4432c620f8d569ef29ca74bad2b7eebd803441'>import: opam: Fix conditions.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2018-12-17 21:43:51 +0100'>2018-12-17</span></td><td><a href='/guix/commit/tests/opam.scm?id=cce654fabdf09cac7d18f9bad842ba8445aa022c'>import: Update opam importer.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>
<tr><td><span title='2018-09-04 17:25:11 +0200'>2018-09-04</span></td><td><a href='/guix/commit/tests/opam.scm?id=ca719424455465fca4b872c371daf2a46de88b33'>Switch to Guile-Gcrypt.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-07-10 10:11:01 +0200'>2018-07-10</span></td><td><a href='/guix/commit/tests/opam.scm?id=b24443bff9f9f3f36353eea2ef35e6dc3745a417'>guix: Add opam importer.</a><span class='msg-avail'>...</span></td><td>Julien Lepiller</td></tr>