difftool: teach difftool to handle directory diffs

When 'difftool' is called to compare a range of commits that modify
more than one file, it opens a separate instance of the diff tool for
each file that changed.

The new '--dir-diff' option copies all the modified files to a temporary
location and runs a directory diff on them in a single instance of the
diff tool.

Signed-off-by: Tim Henigan <tim.henigan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
difftool: print list of valid tools with '--tool-help'

Since bc7a96a (mergetool--lib: Refactor tools into separate files,
2011-08-18), it is possible to add a new diff tool by creating a simple
script in the '$(git --exec-path)/mergetools' directory.  Updating the
difftool help text is still a manual process, and the documentation can
easily go out of sync.

This commit teaches difftool the '--tool-help' option, which:
  - Reads the list of valid tools from 'mergetools/*'
  - Determines which of them are actually installed
  - Determines which are capable of diffing (i.e. not just a merge tool)
  - Prints the resulting list for the user

Signed-off-by: Tim Henigan <tim.henigan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Merge branch 'da/difftool-test' into jch

Makes sure "difftool" options can be given in any order.

* da/difftool-test:
  t7800: Test difftool passing arguments to diff
Merge branch 'jn/diffstat-tests' into jch

Some tests checked the "diff --stat" output when they do not have to,
which unnecessarily made things harder to verify under GETTEXT_POISON.

Not urgent.

* jn/diffstat-tests:
  diffstat summary line varies by locale: miscellany
  test: use numstat instead of diffstat in binary-diff test
  test: use --numstat instead of --stat in "git stash show" tests
  test: test cherry-pick functionality and output separately
  test: modernize funny-names test style
  test: use numstat instead of diffstat in funny-names test
  test: use test_i18ncmp when checking --stat output
Merge branch 'jc/commit-hook-authorship' into jch

"git commit --author=$name" did not tell the name that was being
recorded in the resulting commit to hooks, even though it does do so
when the end user overrode the authorship via the "GIT_AUTHOR_NAME"
environment variable.  This is a simpler of the two approaches.

Will defer til 1.7.10.

* jc/commit-hook-authorship:
  commit: pass author/committer info to hooks
  t7503: does pre-commit-hook learn authorship?
  ident.c: add split_ident_line() to parse formatted ident line
Merge branch 'tr/maint-word-diff-regex-sticky' into jch

The regexp configured with wordregex was incorrectly reused across
files.
Not urgent.

* tr/maint-word-diff-regex-sticky:
  diff: tweak a _copy_ of diff_options with word-diff
  diff: refactor the word-diff setup from builtin_diff_cmd
  t4034: diff.*.wordregex should not be "sticky" in --word-diff
Merge branch 'jh/notes-merge-in-git-dir-worktree' into jch

Running "notes merge --commit" failed to perform correctly when run
from any directory inside $GIT_DIR/.  When "notes merge" stops with
conflicts, $GIT_DIR/NOTES_MERGE_WORKTREE is the place a user edits
to resolve it.

Not urgent.

* jh/notes-merge-in-git-dir-worktree:
  notes-merge: Don't remove .git/NOTES_MERGE_WORKTREE; it may be the user's cwd
  notes-merge: use opendir/readdir instead of using read_directory()
  t3310: illustrate failure to "notes merge --commit" inside $GIT_DIR/
  remove_dir_recursively(): Add flag for skipping removal of toplevel dir
Merge branch 'jc/maint-clean-nested-worktree-in-subdir' into jch

"git clean -d -f" (not "-d -f -f") is supposed to protect nested working
trees of independent git repositories that exist in the current project
working tree from getting removed, but the protection applied only to such
working trees that are at the top-level of the current project by mistake.

Not urgent.

* jc/maint-clean-nested-worktree-in-subdir:
  clean: preserve nested git worktree in subdirectories
Merge branch 'rs/unpack-trees-leakfix' into jch

Will defer til 1.7.10.

* rs/unpack-trees-leakfix:
  unpack-trees: plug minor memory leak
Merge branch 'jc/diff-algo-cleanup' into jch

Resurrects the preparatory clean-up patches from another topic that was
discarded, as this would give a saner foundation to build on diff.algo
configuration option series.

Not urgent.

* jc/diff-algo-cleanup:
  xdiff: PATIENCE/HISTOGRAM are not independent option bits
  xdiff: remove XDL_PATCH_* macros
Merge branch 'nd/stream-more' into jch

Use API to read blob data in smaller chunks in more places to
reduce the memory footprint.  In general, looked fairly good.

Will defer til 1.7.10.

* nd/stream-more:
  update-server-info: respect core.bigfilethreshold
  fsck: use streaming API for writing lost-found blobs
  show: use streaming API for showing blobs
  parse_object: avoid putting whole blob in core
  cat-file: use streaming API to print blobs
  Add more large blob test cases
  streaming: make streaming-write-entry to be more reusable
Merge branch 'zj/test-cred-helper-nicer-prove' into jch

Minor improvement to t0303.
Not urgent.

* zj/test-cred-helper-nicer-prove:
  t0303: resurrect commit message as test documentation
  t0303: immediately bail out w/o GIT_TEST_CREDENTIAL_HELPER
Merge branch 'nl/rebase-i-cheat-sheet' into jch

Not urgent.

* nl/rebase-i-cheat-sheet:
  rebase -i: remind that the lines are top-to-bottom
Merge branch 'nl/http-proxy-more' into jch

The code to talk to http proxies learn to use the same credential
API used to talk to the final http destinations.

Will defer til 1.7.10.

* nl/http-proxy-more:
  http: rename HTTP_REAUTH to HTTP_AUTH_RETRY
  http: Avoid limit of retrying request only twice
  http: handle proxy authentication failure (error 407)
  http: handle proxy proactive authentication
  http: try http_proxy env var when http.proxy config option is not set
Merge branch 'ct/advise-push-default' into jch

Breaks down the cases in which "git push" fails due to non-ff into three
categories, and gives separate advise messages.  This should be a good
change regardless of mm/push-default-switch-warning topic.

* ct/advise-push-default:
  clean up struct ref's nonfastforward field
  push: Provide situational hints for non-fast-forward errors
Merge branch 'mm/push-default-switch-warning' into jch

Not urgent.

This resurrects an ancient patch I wrote during a discussion we had in the
1.6.3-1.6.4 era.  This should probably come after ct/advise-push-default
topic and at that point the advise messages need to be rephrased, taking
the future default change into account.

* mm/push-default-switch-warning:
  push: start warning upcoming default change for push.default

Conflicts:
	builtin/push.c
run-command: treat inaccessible directories as ENOENT

When execvp reports EACCES, it can be one of two things:

  1. We found a file to execute, but did not have
     permissions to do so.

  2. We did not have permissions to look in some directory
     in the $PATH.

In the former case, we want to consider this a
permissions problem and report it to the user as such (since
getting this for something like "git foo" is likely a
configuration error).

In the latter case, there is a good chance that the
inaccessible directory does not contain anything of
interest. Reporting "permission denied" is confusing to the
user (and prevents our usual "did you mean...?" lookup). It
also prevents git from trying alias lookup, since we do so
only when an external command does not exist (not when it
exists but has an error).

This patch detects EACCES from execvp, checks whether we are
in case (2), and if so converts errno to ENOENT. This
behavior matches that of "bash" (but not of simpler shells
that use execvp more directly, like "dash").

Test stolen from Junio.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
push: detect nonsense "upstream" check more carefully

The user can say "git push" without specifying any refspec.  When using
"upstream" semantics via the push.default configuration, the user wants to
update the "upstream" branch, which is the branch at a remote repository
the current branch is set to integrate with, with this command.

There are cases that "git push" do not make sense when push.default is set
to "upstream":

 - The current branch does not have branch.$name.remote configured.  By
   definition, "git push" that does not name where to push to will not
   know where to push to.  The user may explicitly say "git push $there",
   but again, by definition, no branch at repository $there is set to
   integrate with the current branch in this case and we wouldn't know
   which remote branch to update.

 - The current branch does have branch.$name.remote configured, but it
   does not specify branch.$name.merge that names what branch at the
   remote this branch integrates with. "git push" knows where to push in
   this case (or the user may explicitly say "git push $remote" to tell us
   where to push), but we do not know which remote branch to update.

 - The current branch does have both branch.$name.remote and
   branch.$name.merge configured, but the user said "git push $there",
   where $there does not match what "branch.$name.remote" is configured
   to.  By definition, no branch at repository $there is set to integrate
   with the current branch in this case and we wouldn't know which remote
   branch to update.

The first two cases were already checked correctly, but the third case was
not checked and we ended up updating the branch named branch.$name.merge
at repository $there, which was totally bogus.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
[fixup] remove misguided "try to see if URLs are the same"

Signed-off-by: Junio C Hamano <gitster@pobox.com>
varint: make it available outside the context of pack

Signed-off-by: Junio C Hamano <gitster@pobox.com>