perf-test: update corpus signature

In the decade (!) since this corpus was last updated, the keyserver
network is essentially dead, and I have migrated gpg keys. Bump the
version number as a clean way of switching signatures. Also update the
instructions to suggest using "--locate-external-key" to download the
public key. By default this uses WKD, which is now supported for my
UID.

performance-test/README

@@ -24,11 +24,11 @@ Getting set up to run tests:
 First, you need to get the corpus.  If you don't already have the gpg
 key for David Bremner, run
 
-   % gpg --search 'david@tethera.net'
+   % gpg --locate-external-key 'david@tethera.net'
 
 This should get you a key with fingerprint
 
-    815B 6398 2A79 F8E7 C727  86C4 762B 57BB 7842 06AD
+    7A18 807F 100A 4570 C596  8420 7E4E 65C8 720B 706B
 
 (the last 8 digits are printed as the "key id").
 

performance-test/download/notmuch-email-corpus-0.5.tar.xz.asc

@@ -0,0 +1,16 @@
+-----BEGIN PGP SIGNATURE-----
+
+iQIzBAABCAAdFiEEkiyHYXwaY0SiY6fqA0U5G1WqFSEFAmR119gACgkQA0U5G1Wq
+FSHlSQ/+NSRj27PEZjaP2I+3j+rsMG3pnVckNcuOQyfgjJ+zEagMZyRu3vaIA/pX
+xtBrNIX4l4CQIkqwyNjsuqJdzh6S3DeCWSEr1Q+GSBki+wQCBiRuDYY2HQoDezEK
+4bMfniEWZpKJD8PfIabz0OOqMUsfXEYMd9kefew5/J4OGnDIv8E5pKfqvDNNO4rW
+MhZ9w9uR9wkvmfmpO66kAgTfLllwiyNHWoWnzQfNmqM8eULFn7XxM1PEZShUEqXf
+pTWCqqm5OyUcy8f+gy9Mb7DRRvnwLpHHRQlCzzH2c+ENQRpt1ErsgVKpHTVk4UsB
+EML+zwyWEaQg7xVKWXRJDuGCF47S1GCQNUtvtx57HJl6Ds6N2mlr2KEGaI7qtiz5
+5hdaTc0L/TVN0WS+uCdfdDDozFErf1kwhA6Jnpi0YNNdK+wpFzj7ISvA+DNHwJ75
+TLBuJIU/h3QfX3NDC5xDbsWAgpv7a84e7ePO6+kAVkHsNYDbFjiunr5fRbqDsJcJ
+B+aVGhKvFZbziC84Dn5Ae9Lpa40fQlxbdb+So2nDIiuR3P33vt7wr/e2ptVfrqkn
+a1DM96n03VWexwEDMye3b3rOTXsN5Ul87zucg9xWm5JT75NGuqJ1WDJN/wwNPDro
+ZXS1OHh7UKsU1tP2J9+gLiKYNBP4m4BQjEgYXpiYEoge9A1QplQ=
+=5/Ep
+-----END PGP SIGNATURE-----

performance-test/version.sh

@@ -1,3 +1,3 @@
 # this should be both a valid Makefile fragment and valid POSIX(ish) shell.
 
-PERFTEST_VERSION=0.4
+PERFTEST_VERSION=0.5