Make GnuPG automatically find a pinentry installed by Guix. Try using
$HOME or, if that variable is not set, use the system password database,
or fall back to looking in "/".

More information:

https://bugs.gnu.org/24076

diff --git a/common/homedir.c b/common/homedir.c
index 4b6e46e88..f7ae68ba5 100644
--- a/common/homedir.c
+++ b/common/homedir.c
@@ -33,6 +33,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <unistd.h>
+#include <pwd.h>
 
 #ifdef HAVE_W32_SYSTEM
 #include <winsock2.h>   /* Due to the stupid mingw64 requirement to
@@ -67,6 +68,10 @@
  * gnupg_homedir and gnupg_set_homedir.  Malloced.  */
 static char *the_gnupg_homedir;
 
+/* The user's home directory. Used in Guix to help GnuPG find the
+ * pinentry. */
+static char *the_user_homedir;
+
 /* Flag indicating that home directory is not the default one.  */
 static byte non_default_homedir;
 
@@ -509,6 +514,25 @@ gnupg_homedir (void)
   return the_gnupg_homedir;
 }
 
+/* Return the user's home directory */
+const char *
+user_homedir (void)
+{
+  const char *dir;
+  dir = getenv("HOME");
+  if (dir == NULL)
+    {
+       struct passwd *pw = NULL;
+       pw = getpwuid (getuid ());
+       if (pw != NULL)
+         dir = pw->pw_dir;
+       else
+         dir = "/";
+    }
+  if (!the_user_homedir)
+    the_user_homedir = make_absfilename (dir, NULL);
+  return the_user_homedir;
+}
 
 /* Return whether the home dir is the default one.  */
 int
@@ -971,6 +995,7 @@ get_default_pinentry_name (int reset)
   } names[] = {
     /* The first entry is what we return in case we found no
        other pinentry.  */
+    { user_homedir, "/.guix-profile/bin/pinentry" },
     { gnupg_bindir, DIRSEP_S "pinentry" EXEEXT_S },
 #ifdef HAVE_W32_SYSTEM
     /* Try Gpg4win directory (with bin and without.) */
ge'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=c5ea9598d88b1951c858f6d91628c495f8411257'>root</a>/<a href='/guix/log/tests?id=c5ea9598d88b1951c858f6d91628c495f8411257'>tests</a>/<a href='/guix/log/tests/cve.scm?id=c5ea9598d88b1951c858f6d91628c495f8411257'>cve.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/tests/cve.scm?id=c5ea9598d88b1951c858f6d91628c495f8411257&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2019-10-23 16:40:17 +0200'>2019-10-23</span></td><td><a href='/guix/commit/tests/cve.scm?id=74afaa37d5dec1a9d1b83951529ba69d8947fb07'>cve: Rewrite to read the JSON feed instead of the XML feed.</a><span class='msg-avail'>...<span class='msg-tooltip'>The XML feed was discontinued on Oct. 16th, 2019:

  &lt;https://nvd.nist.gov/General/News/XML-Vulnerability-Feed-Retirement-Phase-3&gt;

* guix/cve.scm (string-&gt;date*): New procedure.
(&lt;cve-item&gt;, &lt;cve&gt;, &lt;cve-reference&gt;): New record types.
(cpe-match-&gt;cve-configuration, configuration-data-&gt;cve-configurations)
(json-&gt;cve-items, version-matches?): New procedures.
(yearly-feed-uri): Change URL to refer to JSON feed.
(cpe-&gt;product-alist, %parse-vulnerability-feed)
(xml-&gt;vulnerabilities): Remove.
(cve-configuration-&gt;package-list, merge-package-lists)
(cve-item-&gt;vulnerability, json-&gt;vulnerabilities): New procedures.
(write-cache): Use 'json-&gt;vulnerabilities' instead of
'xml-&gt;vulnerabilities', and remove 'parameterize'.
(vulnerabilities-&gt;lookup-proc): Use 'version-matches?' when VERSION is
true.
* tests/cve.scm (%sample): Use 'tests/cve-sample.json'.
(%expected-vulnerabilities): Rewrite accordingly.
("json-&gt;cve-items", "cve-item-published-date")
("json-&gt;vulnerabilities"): New tests.
("xml-&gt;vulnerabilities"): Remove.
("vulnerabilities-&gt;lookup-proc"): Adjust to new vulnerabilities.
* tests/cve-sample.json: New file.
* tests/cve-sample.xml: Remove.
* Makefile.am (EXTRA_DIST): Adjust accordingly.
* doc/guix.texi (Invoking guix lint): Update nist.gov URLs.
</span></span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2019-10-20 23:26:50 +0200'>2019-10-20</span></td><td><a href='/guix/commit/tests/cve.scm?id=79c03e55e26d88c8d327daced02367abe7f17f91'>tests: Avoid now-deprecated 'make-struct'.</a><span class='msg-avail'>...<span class='msg-tooltip'>* tests/cve.scm (vulnerability): Use 'make-struct/no-tail' instead of
'make-struct', which is deprecated.
* tests/lint.scm ("cve: one vulnerability")
("cve: one patched vulnerability")
("cve: known safe from vulnerability")
("cve: vulnerability fixed in replacement version")
("cve: patched vulnerability in replacement"): Likewise.
</span></span></td><td>Ludovic Courtès</td></tr>