Merge branch 'pw/use-in-process-checkout-in-rebase'

Use an internal call to reset_head() helper function instead of
spawning "git checkout" in "rebase", and update code paths that are
involved in the change.

* pw/use-in-process-checkout-in-rebase:
  rebase -m: don't fork git checkout
  rebase --apply: set ORIG_HEAD correctly
  rebase --apply: fix reflog
  reset_head(): take struct rebase_head_opts
  rebase: cleanup reset_head() calls
  create_autostash(): remove unneeded parameter
  reset_head(): make default_reflog_action optional
  reset_head(): factor out ref updates
  reset_head(): remove action parameter
  rebase --apply: don't run post-checkout hook if there is an error
  rebase: do not remove untracked files on checkout
  rebase: pass correct arguments to post-checkout hook
  t5403: refactor rebase post-checkout hook tests
  rebase: factor out checkout for up to date branch

diff --cc builtin/merge.c
Simple merge

diff --cc builtin/rebase.c
Simple merge

diff --cc reset.c
index 0881e63691508c5c965620eda574d18fdd295789,448cb3fd78576ed72f0415f2d3b0bdfc3b60a8a4..e3383a93343e3df16ee9eda6ee7886a49e980a1a
--- 1/reset.c
--- 2/reset.c
+++ b/reset.c
@@@ -7,19 -7,83 +7,84 @@@
  #include "tree-walk.h"
  #include "tree.h"
  #include "unpack-trees.h"
 +#include "hook.h"
  
- int reset_head(struct repository *r, struct object_id *oid, const char *action,
-              const char *switch_to_branch, unsigned flags,
-              const char *reflog_orig_head, const char *reflog_head,
-              const char *default_reflog_action)
+ static int update_refs(const struct reset_head_opts *opts,
+                      const struct object_id *oid,
+                      const struct object_id *head)
  {
-       unsigned detach_head = flags & RESET_HEAD_DETACH;
-       unsigned reset_hard = flags & RESET_HEAD_HARD;
-       unsigned run_hook = flags & RESET_HEAD_RUN_POST_CHECKOUT_HOOK;
-       unsigned refs_only = flags & RESET_HEAD_REFS_ONLY;
-       unsigned update_orig_head = flags & RESET_ORIG_HEAD;
-       struct object_id head_oid;
+       unsigned detach_head = opts->flags & RESET_HEAD_DETACH;
+       unsigned run_hook = opts->flags & RESET_HEAD_RUN_POST_CHECKOUT_HOOK;
+       unsigned update_orig_head = opts->flags & RESET_ORIG_HEAD;
+       const struct object_id *orig_head = opts->orig_head;
+       const char *switch_to_branch = opts->branch;
+       const char *reflog_branch = opts->branch_msg;
+       const char *reflog_head = opts->head_msg;
+       const char *reflog_orig_head = opts->orig_head_msg;
+       const char *default_reflog_action = opts->default_reflog_action;
+       struct object_id *old_orig = NULL, oid_old_orig;
+       struct strbuf msg = STRBUF_INIT;
+       const char *reflog_action;
+       size_t prefix_len;
+       int ret;
+ 
+       if ((update_orig_head && !reflog_orig_head) || !reflog_head) {
+               if (!default_reflog_action)
+                       BUG("default_reflog_action must be given when reflog messages are omitted");
+               reflog_action = getenv(GIT_REFLOG_ACTION_ENVIRONMENT);
+               strbuf_addf(&msg, "%s: ", reflog_action ? reflog_action :
+                                                         default_reflog_action);
+       }
+       prefix_len = msg.len;
+ 
+       if (update_orig_head) {
+               if (!get_oid("ORIG_HEAD", &oid_old_orig))
+                       old_orig = &oid_old_orig;
+               if (head) {
+                       if (!reflog_orig_head) {
+                               strbuf_addstr(&msg, "updating ORIG_HEAD");
+                               reflog_orig_head = msg.buf;
+                       }
+                       update_ref(reflog_orig_head, "ORIG_HEAD",
+                                  orig_head ? orig_head : head,
+                                  old_orig, 0, UPDATE_REFS_MSG_ON_ERR);
+               } else if (old_orig)
+                       delete_ref(NULL, "ORIG_HEAD", old_orig, 0);
+       }
+ 
+       if (!reflog_head) {
+               strbuf_setlen(&msg, prefix_len);
+               strbuf_addstr(&msg, "updating HEAD");
+               reflog_head = msg.buf;
+       }
+       if (!switch_to_branch)
+               ret = update_ref(reflog_head, "HEAD", oid, head,
+                                detach_head ? REF_NO_DEREF : 0,
+                                UPDATE_REFS_MSG_ON_ERR);
+       else {
+               ret = update_ref(reflog_branch ? reflog_branch : reflog_head,
+                                switch_to_branch, oid, NULL, 0,
+                                UPDATE_REFS_MSG_ON_ERR);
+               if (!ret)
+                       ret = create_symref("HEAD", switch_to_branch,
+                                           reflog_head);
+       }
+       if (!ret && run_hook)
 -              run_hook_le(NULL, "post-checkout",
++              run_hooks_l("post-checkout",
+                           oid_to_hex(head ? head : null_oid()),
+                           oid_to_hex(oid), "1", NULL);
+       strbuf_release(&msg);
+       return ret;
+ }
+ 
+ int reset_head(struct repository *r, const struct reset_head_opts *opts)
+ {
+       const struct object_id *oid = opts->oid;
+       const char *switch_to_branch = opts->branch;
+       unsigned reset_hard = opts->flags & RESET_HEAD_HARD;
+       unsigned refs_only = opts->flags & RESET_HEAD_REFS_ONLY;
+       unsigned update_orig_head = opts->flags & RESET_ORIG_HEAD;
+       struct object_id *head = NULL, head_oid;
        struct tree_desc desc[2] = { { NULL }, { NULL } };
        struct lock_file lock = LOCK_INIT;
        struct unpack_trees_options unpack_tree_opts = { 0 };

diff --cc sequencer.c
Simple merge