Documentation/difftool: add deltawalker to list of valid diff tools

deltawalker has been supported since 284a126c3ef3, but was not added
to the list of valid diff tools reported by 'git difftool --help'.

Signed-off-by: Tim Henigan <tim.henigan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
fetch/receive: remove over-pessimistic connectivity check

Git 1.7.8 introduced an object and history re-validation step after
"fetch" or "push" causes new history to be added to a receiving
repository. This is to protect a malicious server or pushing client from
corrupting the repository by taking advantage of an existing corrupt
object that is unconnected to existing history.

But this check is way over-pessimistic.  During "fetch" or "receive-pack"
(the server side of "push"), unpack-objects and index-pack already
validate individual objects that are received, and the only thing we would
want to catch are corrupted objects that already happen to exist in our
repository but are not referenced from our refs.  Such objects must have
been written by an earlier run of our codepaths that write out loose
objects or packfiles, and they must have done the validation of individual
objects when they did so.  The only thing left to worry about is the
connectivity integrity, which can be checked with "rev-list --objects",
which is much cheaper.  We have been paying the 5x to 8x runtime overhead
the --verify-objects often adds for no real gain.

Revert check_everything_connected() not to use this over-pessimistic
check.

Credit goes to Nguyễn Thái Ngọc Duy, who originally identified the
performance regression and endured multiple rounds of reviews to fix it.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge branch 'th/doc-diff-submodule-option'

* th/doc-diff-submodule-option:
  Documentation/diff-options: reword description of --submodule option
Merge branch 'th/git-diffall'

* th/git-diffall:
  contrib/diffall: fix cleanup trap on Windows
  contrib/diffall: eliminate duplicate while loops
  contrib/diffall: eliminate use of tar
  contrib/diffall: create tmp dirs without mktemp
  contrib/diffall: comment actual reason for 'cdup'
Merge branch 'master' into next

* master:
Merge branch 'th/mergetools-deltawalker' into next

* th/mergetools-deltawalker:
  Documentation/difftool: add deltawalker to list of valid diff tools
Merge branch 'jc/maint-verify-objects-remove-pessimism' into next

The code to validate the history connectivity between old refs and new
refs used by fetch and receive-pack, introduced in 1.7.8, was grossly
inefficient and unnecessarily tried to re-validate integrity of individual
objects. This essentially reverts that performance regression.

* jc/maint-verify-objects-remove-pessimism:
  fetch/receive: remove over-pessimistic connectivity check
Merge branch 'sl/customize-sane-tool-path' into next

Would be nice to hear from people who actually use autoconf, either
on Solaris or other platforms.

* sl/customize-sane-tool-path:
  configure: allow user to prevent $PATH "sanitization" on Solaris
Merge branch 'jn/maint-fast-import-empty-ls' into next

fast-import did not diagnose "ls ''" that asks an empty path
as an error.

* jn/maint-fast-import-empty-ls:
  fast-import: don't allow 'ls' of path with empty components
  fast-import: leakfix for 'ls' of dirty trees
Merge branch 'jc/diff-algo-cleanup' into next

Resurrects the preparatory clean-up patches from another topic
that was discarded.

* jc/diff-algo-cleanup:
  xdiff: PATIENCE/HISTOGRAM are not independent option bits
  xdiff: remove XDL_PATCH_* macros