Code clean-up.

* en/merge-cleanup:
  merge-recursive: rename merge_file_1() and merge_content()
  merge-recursive: remove final remaining caller of merge_file_one()
  merge-recursive: avoid wrapper function when unnecessary and wasteful
  merge-recursive: set paths correctly when three-way merging content

Header files clean-up.

* rj/header-check:
  delta-islands.h: add missing forward declarations (hdr-check)
  midx.h: add missing forward declarations (hdr-check)
  refs/refs-internal.h: add missing declarations (hdr-check)
  refs/packed-backend.h: add missing declaration (hdr-check)
  refs/ref-cache.h: add missing declarations (hdr-check)
  ewah/ewok_rlw.h: add missing include (hdr-check)
  json-writer.h: add missing include (hdr-check)
  Makefile: add a hdr-check target

Doc update.

* ma/config-doc-update:
  git-config.txt: fix 'see: above' note
  Doc: use `--type=bool` instead of `--bool`

Fix interactions between two recent topics.

* jk/delta-islands-with-bitmap-reuse-delta-fix:
  pack-objects: handle island check for "external" delta base

Fix for typo in a sample code in comment.

* tq/refs-internal-comment-fix:
  refs: docstring typo

An alias that expands to another alias has so far been forbidden,
but now it is allowed to create such an alias.

* ts/alias-of-alias:
  t0014: introduce an alias testing suite
  alias: show the call history when an alias is looping
  alias: add support for aliases of an alias

The recently introduced commit-graph auxiliary data is incompatible
with mechanisms such as replace & grafts that "breaks" immutable
nature of the object reference relationship.  Disable optimizations
based on its use (and updating existing commit-graph) when these
incompatible features are in use in the repository.

* ds/commit-graph-with-grafts:
  commit-graph: close_commit_graph before shallow walk
  commit-graph: not compatible with uninitialized repo
  commit-graph: not compatible with grafts
  commit-graph: not compatible with replace objects
  test-repository: properly init repo
  commit-graph: update design document
  refs.c: upgrade for_each_replace_ref to be a each_repo_ref_fn callback
  refs.c: migrate internal ref iteration to pass thru repository argument

Generation of (experimental) commit-graph files have so far been
fairly silent, even though it takes noticeable amount of time in a
meaningfully large repository.  The users will now see progress
output.

* ab/commit-graph-progress:
  gc: fix regression in 7b0f2292 impacting --quiet
  commit-graph verify: add progress output
  commit-graph write: add progress output

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

Update fsck.skipList implementation and documentation.

* ab/fsck-skiplist:
  fsck: support comments & empty lines in skipList
  fsck: use oidset instead of oid_array for skipList
  fsck: use strbuf_getline() to read skiplist file
  fsck: add a performance test for skipList
  fsck: add a performance test
  fsck: document that skipList input must be unabbreviated
  fsck: document and test commented & empty line skipList input
  fsck: document and test sorted skipList input
  fsck tests: add a test for no skipList input
  fsck tests: setup of bogus commit object

"git multi-pack-index" learned to detect corruption in the .midx
file it uses, and this feature has been integrated into "git fsck".

* ds/multi-pack-verify:
  fsck: verify multi-pack-index
  multi-pack-index: report progress during 'verify'
  multi-pack-index: verify object offsets
  multi-pack-index: fix 32-bit vs 64-bit size check
  multi-pack-index: verify oid lookup order
  multi-pack-index: verify oid fanout order
  multi-pack-index: verify missing pack
  multi-pack-index: verify packname order
  multi-pack-index: verify corrupt chunk lookup table
  multi-pack-index: verify bad header
  multi-pack-index: add 'verify' verb

Various tests have been updated to make it easier to swap the
hash function used for object identification.

* bc/hash-independent-tests:
  t5318: use test_oid for HASH_LEN
  t1407: make hash size independent
  t1406: make hash-size independent
  t1405: make hash size independent
  t1400: switch hard-coded object ID to variable
  t1006: make hash size independent
  t0064: make hash size independent
  t0002: abstract away SHA-1 specific constants
  t0000: update tests for SHA-256
  t0000: use hash translation table
  t: add test functions to translate hash-related values

Test helper binaries clean-up.

* nd/test-tool:
  Makefile: add a hint about TEST_BUILTINS_OBJS
  t/helper: merge test-dump-fsmonitor into test-tool
  t/helper: merge test-parse-options into test-tool
  t/helper: merge test-pkt-line into test-tool
  t/helper: merge test-dump-untracked-cache into test-tool
  t/helper: keep test-tool command list sorted

Split Documentation/config.txt for easier maintenance.

* nd/config-split:
  config.txt: move submodule part out to a separate file
  config.txt: move sequence.editor out of "core" part
  config.txt: move sendemail part out to a separate file
  config.txt: move receive part out to a separate file
  config.txt: move push part out to a separate file
  config.txt: move pull part out to a separate file
  config.txt: move gui part out to a separate file
  config.txt: move gitcvs part out to a separate file
  config.txt: move format part out to a separate file
  config.txt: move fetch part out to a separate file
  config.txt: follow camelCase naming

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

* maint:
  Git 2.19.1
  Git 2.18.1
  Git 2.17.2
  fsck: detect submodule paths starting with dash
  fsck: detect submodule urls starting with dash
  Git 2.16.5
  Git 2.15.3
  Git 2.14.5
  submodule-config: ban submodule paths that start with a dash
  submodule-config: ban submodule urls that start with dash
  submodule--helper: use "--" to signal end of clone options

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

* maint-2.18:
  Git 2.18.1
  Git 2.17.2
  fsck: detect submodule paths starting with dash
  fsck: detect submodule urls starting with dash
  Git 2.16.5
  Git 2.15.3
  Git 2.14.5
  submodule-config: ban submodule paths that start with a dash
  submodule-config: ban submodule urls that start with dash
  submodule--helper: use "--" to signal end of clone options

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

* maint-2.17:
  Git 2.17.2
  fsck: detect submodule paths starting with dash
  fsck: detect submodule urls starting with dash
  Git 2.16.5
  Git 2.15.3
  Git 2.14.5
  submodule-config: ban submodule paths that start with a dash
  submodule-config: ban submodule urls that start with dash
  submodule--helper: use "--" to signal end of clone options

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

As with urls, submodule paths with dashes are ignored by
git, but may end up confusing older versions. Detecting them
via fsck lets us prevent modern versions of git from being a
vector to spread broken .gitmodules to older versions.

Compared to blocking leading-dash urls, though, this
detection may be less of a good idea:

  1. While such paths provide confusing and broken results,
     they don't seem to actually work as option injections
     against anything except "cd". In particular, the
     submodule code seems to canonicalize to an absolute
     path before running "git clone" (so it passes
     /your/clone/-sub).

  2. It's more likely that we may one day make such names
     actually work correctly. Even after we revert this fsck
     check, it will continue to be a hassle until hosting
     servers are all updated.

On the other hand, it's not entirely clear that the behavior
in older versions is safe. And if we do want to eventually
allow this, we may end up doing so with a special syntax
anyway (e.g., writing "./-sub" in the .gitmodules file, and
teaching the submodule code to canonicalize it when
comparing).

So on balance, this is probably a good protection.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Urls with leading dashes can cause mischief on older
versions of Git. We should detect them so that they can be
rejected by receive.fsckObjects, preventing modern versions
of git from being a vector by which attacks can spread.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

* maint-2.16:
  Git 2.16.5
  Git 2.15.3
  Git 2.14.5
  submodule-config: ban submodule paths that start with a dash
  submodule-config: ban submodule urls that start with dash
  submodule--helper: use "--" to signal end of clone options

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

* maint-2.15:
  Git 2.15.3
  Git 2.14.5
  submodule-config: ban submodule paths that start with a dash
  submodule-config: ban submodule urls that start with dash
  submodule--helper: use "--" to signal end of clone options

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

* maint-2.14:
  Git 2.14.5
  submodule-config: ban submodule paths that start with a dash
  submodule-config: ban submodule urls that start with dash
  submodule--helper: use "--" to signal end of clone options

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

We recently banned submodule urls that look like
command-line options. This is the matching change to ban
leading-dash paths.

As with the urls, this should not break any use cases that
currently work. Even with our "--" separator passed to
git-clone, git-submodule.sh gets confused. Without the code
portion of this patch, the clone of "-sub" added in t7417
would yield results like:

    /path/to/git-submodule: 410: cd: Illegal option -s
    /path/to/git-submodule: 417: cd: Illegal option -s
    /path/to/git-submodule: 410: cd: Illegal option -s
    /path/to/git-submodule: 417: cd: Illegal option -s
    Fetched in submodule path '-sub', but it did not contain b56243f8f4eb91b2f1f8109452e659f14dd3fbe4. Direct fetching of that commit failed.

Moreover, naively adding such a submodule doesn't work:

  $ git submodule add $url -sub
  The following path is ignored by one of your .gitignore files:
  -sub

even though there is no such ignore pattern (the test script
hacks around this with a well-placed "git mv").

Unlike leading-dash urls, though, it's possible that such a
path _could_ be useful if we eventually made it work. So
this commit should be seen not as recommending a particular
policy, but rather temporarily closing off a broken and
possibly dangerous code-path. We may revisit this decision
later.

There are two minor differences to the tests in t7416 (that
covered urls):

  1. We don't have a "./-sub" escape hatch to make this
     work, since the submodule code expects to be able to
     match canonical index names to the path field (so you
     are free to add submodule config with that path, but we
     would never actually use it, since an index entry would
     never start with "./").

  2. After this patch, cloning actually succeeds. Since we
     ignore the submodule.*.path value, we fail to find a
     config stanza for our submodule at all, and simply
     treat it as inactive. We still check for the "ignoring"
     message.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

The previous commit taught the submodule code to invoke our
"git clone $url $path" with a "--" separator so that we
aren't confused by urls or paths that start with dashes.

However, that's just one code path. It's not clear if there
are others, and it would be an easy mistake to add one in
the future. Moreover, even with the fix in the previous
commit, it's quite hard to actually do anything useful with
such an entry. Any url starting with a dash must fall into
one of three categories:

 - it's meant as a file url, like "-path". But then any
   clone is not going to have the matching path, since it's
   by definition relative inside the newly created clone. If
   you spell it as "./-path", the submodule code sees the
   "/" and translates this to an absolute path, so it at
   least works (assuming the receiver has the same
   filesystem layout as you). But that trick does not apply
   for a bare "-path".

 - it's meant as an ssh url, like "-host:path". But this
   already doesn't work, as we explicitly disallow ssh
   hostnames that begin with a dash (to avoid option
   injection against ssh).

 - it's a remote-helper scheme, like "-scheme::data". This
   _could_ work if the receiver bends over backwards and
   creates a funny-named helper like "git-remote--scheme".
   But normally there would not be any helper that matches.

Since such a url does not work today and is not likely to do
anything useful in the future, let's simply disallow them
entirely. That protects the existing "git clone" path (in a
belt-and-suspenders way), along with any others that might
exist.

Our tests cover two cases:

  1. A file url with "./" continues to work, showing that
     there's an escape hatch for people with truly silly
     repo names.

  2. A url starting with "-" is rejected.

Note that we expect case (2) to fail, but it would have done
so even without this commit, for the reasons given above.
So instead of just expecting failure, let's also check for
the magic word "ignoring" on stderr. That lets us know that
we failed for the right reason.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

When we clone a submodule, we call "git clone $url $path".
But there's nothing to say that those components can't begin
with a dash themselves, confusing git-clone into thinking
they're options. Let's pass "--" to make it clear what we
expect.

There's no test here, because it's actually quite hard to
make these names work, even with "git clone" parsing them
correctly. And we're going to restrict these cases even
further in future commits. So we'll leave off testing until
then; this is just the minimal fix to prevent us from doing
something stupid with a badly formed entry.
Reported-by: Njoernchen <joernchen@phenoelit.de>
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Recently added "range-diff" had a corner-case bug to cause it
segfault, which has been corrected.

* tg/range-diff-corner-case-fix:
  linear-assignment: fix potential out of bounds memory access

Test updates.

* sg/split-index-test:
  t0090: disable GIT_TEST_SPLIT_INDEX for the test checking split index
  t1700-split-index: drop unnecessary 'grep'

"git update-ref" learned to make both "--no-deref" and "--stdin"
work at the same time.

* en/update-ref-no-deref-stdin:
  update-ref: allow --no-deref with --stdin
  update-ref: fix type of update_flags variable to match its usage

Update error messages given by "git remote" and make them consistent.

* ms/remote-error-message-update:
  builtin/remote: quote remote name on error to display empty name

The code to backfill objects in lazily cloned repository did not
work correctly, which has been corrected.

* jt/lazy-object-fetch-fix:
  fetch-object: set exact_oid when fetching
  fetch-object: unify fetch_object[s] functions

"git rebase" etc. in Git 2.19 fails to abort when given an empty
commit log message as result of editing, which has been corrected.

* en/sequencer-empty-edit-result-aborts:
  sequencer: fix --allow-empty-message behavior, make it smarter

Recent update broke the reachability algorithm when refs (e.g.
tags) that point at objects that are not commit were involved,
which has been fixed.

* ds/reachable:
  commit-reach: fix memory and flag leaks
  commit-reach: properly peel tags