Update to JGit 4.0.0.201505191015-rc1.19-g1773002

Use try-with-resources to handle clean upreaders and walk
instances that now use close() instead of release().

Change-Id: I884d87715bdd920f4e9ef82864d5b962a5b3b065

lib/jgit/BUCK

diff --git a/lib/jgit/BUCK b/lib/jgit/BUCK
index ae8ae06..3df8752 100644
--- a/lib/jgit/BUCK
+++ b/lib/jgit/BUCK
@@ -1,10 +1,10 @@
-REPO = MAVEN_CENTRAL
-VERS = '3.6.0.201412230720-r'
+REPO = GERRIT
+VERS = '4.0.0.201505191015-rc1.19-g1773002'
 
 maven_jar(
   name = 'jgit',
   id = 'org.eclipse.jgit:org.eclipse.jgit:' + VERS,
-  sha1 = 'b005b69d9f5b4dba636a95403d5cb62bad5c486d',
+  sha1 = '4db24b39dab8dc0e889807383728032945f461be',
   repository = REPO,
   unsign = True,
   deps = [':ewah'],
@@ -18,7 +18,7 @@
 maven_jar(
   name = 'jgit-servlet',
   id = 'org.eclipse.jgit:org.eclipse.jgit.http.server:' + VERS,
-  sha1 = '92cdf015b62c8a4f8fc1f6fd8b1835931bd4b4d6',
+  sha1 = '7bfdbddea56a87f3f2687ae6abf2c5bdae649f0c',
   repository = REPO,
   deps = [':jgit'],
   unsign = True,
@@ -41,7 +41,7 @@
 maven_jar(
   name = 'jgit-archive_library',
   id = 'org.eclipse.jgit:org.eclipse.jgit.archive:' + VERS,
-  sha1 = '359c1f666e4bdc2db795b6c60a7635f6be929a66',
+  sha1 = '08fce6b89f6d1e78f99869d542d70899f3be9c9f',
   repository = REPO,
   deps = [':jgit'],
   unsign = True,
@@ -54,7 +54,7 @@
 maven_jar(
   name = 'junit',
   id = 'org.eclipse.jgit:org.eclipse.jgit.junit:' + VERS,
-  sha1 = 'cb029dba3fafb329078904028db171d9c460ada8',
+  sha1 = 'a54c16076e6cbdb9113565a82cffa5f268ae8e3b',
   repository = REPO,
   unsign = True,
   deps = [':jgit'],