Merge branch 'pw/checkout-conflict-errorfix'

"git checkout --conflict=bad" reported a bad conflictStyle as if it
were given to a configuration variable; it has been corrected to
report that the command line option is bad.

* pw/checkout-conflict-errorfix:
  checkout: fix interaction between --conflict and --merge
  checkout: cleanup --conflict=<style> parsing
  merge options: add a conflict style member
  merge-ll: introduce LL_MERGE_OPTIONS_INIT
  xdiff-interface: refactor parsing of merge.conflictstyle

diff --cc builtin/checkout.c
index 2e8b0d18f445b1307e264634f69c8ce0a3a5c68a,30d13c9e1482e18ecde12ff40810bedb277b432e..2b6166c284e0dda89b829c88313711d078bd2632
--- 1/builtin/checkout.c
--- 2/builtin/checkout.c
+++ b/builtin/checkout.c
@@@ -1930,8 -1924,9 +1949,7 @@@ int cmd_checkout(int argc, const char *
                OPT_BOOL(0, "overlay", &opts.overlay_mode, N_("use overlay mode (default)")),
                OPT_END()
        };
 -      int ret;
 -      struct branch_info new_branch_info = { 0 };
  
-       memset(&opts, 0, sizeof(opts));
        opts.dwim_new_local_branch = 1;
        opts.switch_branch_doing_nothing_is_ok = 1;
        opts.only_merge_on_switching_branches = 0;
@@@ -1978,8 -1978,9 +1996,7 @@@ int cmd_switch(int argc, const char **a
                         N_("throw away local modifications")),
                OPT_END()
        };
 -      int ret;
 -      struct branch_info new_branch_info = { 0 };
  
-       memset(&opts, 0, sizeof(opts));
        opts.dwim_new_local_branch = 1;
        opts.accept_ref = 1;
        opts.accept_pathspec = 0;
@@@ -2016,8 -2020,9 +2033,7 @@@ int cmd_restore(int argc, const char **
                OPT_BOOL(0, "overlay", &opts.overlay_mode, N_("use overlay mode")),
                OPT_END()
        };
 -      int ret;
 -      struct branch_info new_branch_info = { 0 };
  
-       memset(&opts, 0, sizeof(opts));
        opts.accept_ref = 0;
        opts.accept_pathspec = 1;
        opts.empty_pathspec_ok = 0;

diff --cc merge-ll.c
Simple merge

diff --cc merge-ort.c
Simple merge

diff --cc merge-recursive.c
Simple merge