Bug 1247168 - Configure Mercurial and install global hgrc; r=dustin

web.cacerts matches what the Ubuntu package does by default.

[progress] changes are to make output in TaskCluster logs less
spammy (only 1 update per second instead of up to 10).

The robustcheckout extension will be used in a subsequent commit to
handle repository checkouts.

MozReview-Commit-ID: 2PvW4wEGk2u

--HG--
extra : rebase_source : 742627ba823d4f2097a4273e6cc6af8bb842c69f
extra : histedit_source : d479c1923c71605e9511e877b4b90d3b4d42f542

testing/docker/decision/system-setup.sh

@@ -41,6 +41,40 @@ EOF
 
 dpkg -i mercurial-common_3.8.4_all.deb mercurial_3.8.4_amd64.deb
 
+mkdir -p /usr/local/mercurial
+chown 755 /usr/local/mercurial
+cd /usr/local/mercurial
+tooltool_fetch <<'EOF'
+[
+{
+    "size": 11849,
+    "digest": "c88d9b8afd6649bd28bbacfa654ebefec8087a01d1662004aae088d485edeb03a92df1193d1310c0369d7721f475b974fcd4a911428ec65936f7e40cf1609c49",
+    "algorithm": "sha512",
+    "filename": "robustcheckout.py"
+}
+]
+EOF
+
+chmod 644 /usr/local/mercurial/robustcheckout.py
+
+# Install a global hgrc file with reasonable defaults.
+mkdir -p /etc/mercurial
+cat >/etc/mercurial/hgrc <<EOF
+# By default the progress bar starts after 3s and updates every 0.1s. We
+# change this so it shows and updates every 1.0s.
+[progress]
+delay = 1.0
+refresh = 1.0
+
+[web]
+cacerts = /etc/ssl/certs/ca-certificates.crt
+
+[extensions]
+robustcheckout = /usr/local/mercurial/robustcheckout.py
+EOF
+
+chmod 644 /etc/mercurial/hgrc
+
 # Install node
 tooltool_fetch <<'EOF'
 [