cmake: default to using SHA1DC Upstream git.git has changed their default SHA1 implementation to the collision-detection algorithm SHA1DC in commit e6b07da27 (Makefile: make DC_SHA1 the default, 2017-03-17). To match upstream, align ourselves and switch over to SHA1DC by default.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index bedf858..32f8ac0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -42,7 +42,7 @@ OPTION( PROFILE "Generate profiling information" OFF )
OPTION( ENABLE_TRACE "Enables tracing support" OFF )
OPTION( LIBGIT2_FILENAME "Name of the produced binary" OFF )
-OPTION( USE_SHA1DC "Use SHA-1 with collision detection" OFF )
+OPTION( USE_SHA1DC "Use SHA-1 with collision detection" ON )
OPTION( USE_SSH "Link with libssh to enable SSH support" ON )
OPTION( USE_HTTPS "Enable HTTPS support. Can be set to a specific backend" ON )
OPTION( USE_GSSAPI "Link with libgssapi for SPNEGO auth" OFF )