Code clean-up.

* jk/loose-object-cache-oid:
  prefer "hash mismatch" to "sha1 mismatch"
  sha1-file: avoid "sha1 file" for generic use in messages
  sha1-file: prefer "loose object file" to "sha1 file" in messages
  sha1-file: drop has_sha1_file()
  convert has_sha1_file() callers to has_object_file()
  sha1-file: convert pass-through functions to object_id
  sha1-file: modernize loose header/stream functions
  sha1-file: modernize loose object file functions
  http: use struct object_id instead of bare sha1
  update comment references to sha1_object_info()
  sha1-file: fix outdated sha1 comment references

"git rebase -x $cmd" did not reject multi-line command, even though
the command is incapable of handling such a command.  It now is
rejected upfront.

* pw/rebase-x-sanity-check:
  rebase -x: sanity check command

Prepare to run test suite on Azure Pipeline.

* js/vsts-ci: (22 commits)
  test-date: drop unused parameter to getnanos()
  ci: parallelize testing on Windows
  ci: speed up Windows phase
  tests: optionally skip bin-wrappers/
  t0061: workaround issues with --with-dashes and RUNTIME_PREFIX
  tests: add t/helper/ to the PATH with --with-dashes
  mingw: try to work around issues with the test cleanup
  tests: include detailed trace logs with --write-junit-xml upon failure
  tests: avoid calling Perl just to determine file sizes
  README: add a build badge (status of the Azure Pipelines build)
  mingw: be more generous when wrapping up the setitimer() emulation
  ci: use git-sdk-64-minimal build artifact
  ci: add a Windows job to the Azure Pipelines definition
  Add a build definition for Azure DevOps
  ci/lib.sh: add support for Azure Pipelines
  tests: optionally write results as JUnit-style .xml
  test-date: add a subcommand to measure times in shell scripts
  ci: use a junction on Windows instead of a symlink
  ci: inherit --jobs via MAKEFLAGS in run-build-and-tests
  ci/lib.sh: encapsulate Travis-specific things
  ...

The documentation of "git commit-tree" said that the command
understands "--gpg-sign" in addition to "-S", but the command line
parser did not know about the longhand, which has been corrected.

* br/commit-tree-fully-spelled-gpg-sign-option:
  commit-tree: add missing --gpg-sign flag
  t7510: invoke git as part of &&-chain

"git submodule update" learned to abort early when core.worktree
for the submodule is not set correctly to prevent spreading damage.

* sb/submodule-abort-update-upon-config-failure:
  git-submodule: abort if core.worktree could not be set correctly

The travis CI scripts have been corrected to build Git with the
compiler(s) of our choice.

* sg/travis-specific-cc:
  travis-ci: build with the right compiler
  travis-ci: switch to Xcode 10.1 macOS image
  travis-ci: don't be '--quiet' when running the tests
  .gitignore: ignore external debug symbols from GCC on macOS

"git pack-objects" learned another algorithm to compute the set of
objects to send, that trades the resulting packfile off to save
traversal cost to favor small pushes.

* ds/push-sparse-tree-walk:
  pack-objects: create GIT_TEST_PACK_SPARSE
  pack-objects: create pack.useSparse setting
  revision: implement sparse algorithm
  list-objects: consume sparse tree walk
  revision: add mark_tree_uninteresting_sparse

The test lint learned to catch non-portable "sed" options.

* tb/test-lint-sed-options:
  test-lint: only use only sed [-n] [-e command] [-f command_file]

A new date format "--date=human" that morphs its output depending
on how far the time is from the current time has been introduced.
"--date=auto" can be used to use this new format when the output is
going to the pager or to the terminal and otherwise the default
format.

* lt/date-human:
  Add `human` date format tests.
  Add `human` format to test-tool
  Add 'human' date format documentation
  Replace the proposed 'auto' mode with 'auto:'
  Add 'human' date format

Documentation around core.crlf has been updated.

* jk/autocrlf-overrides-eol-doc:
  docs/config: clarify "text property" in core.eol
  doc/gitattributes: clarify "autocrlf overrides eol"

Code cleanup.

* jk/unused-parameter-cleanup:
  convert: drop path parameter from actual conversion functions
  convert: drop len parameter from conversion checks
  config: drop unused parameter from maybe_remove_section()
  show_date_relative(): drop unused "tz" parameter
  column: drop unused "opts" parameter in item_length()
  create_bundle(): drop unused "header" parameter
  apply: drop unused "def" parameter from find_name_gnu()
  match-trees: drop unused path parameter from score functions

The assumption to work on the single "in-core index" instance has
been reduced from the library-ish part of the codebase.

* nd/the-index-final:
  cache.h: flip NO_THE_INDEX_COMPATIBILITY_MACROS switch
  read-cache.c: remove the_* from index_has_changes()
  merge-recursive.c: remove implicit dependency on the_repository
  merge-recursive.c: remove implicit dependency on the_index
  sha1-name.c: remove implicit dependency on the_index
  read-cache.c: replace update_index_if_able with repo_&
  read-cache.c: kill read_index()
  checkout: avoid the_index when possible
  repository.c: replace hold_locked_index() with repo_hold_locked_index()
  notes-utils.c: remove the_repository references
  grep: use grep_opt->repo instead of explict repo argument

Instead of going through "git-rebase--am" scriptlet to use the "am"
backend, the built-in version of "git rebase" learned to drive the
"am" backend directly.

* js/rebase-am:
  built-in rebase: call `git am` directly
  rebase: teach `reset_head()` to optionally skip the worktree
  rebase: avoid double reflog entry when switching branches
  rebase: move `reset_head()` into a better spot

More code in "git bisect" has been rewritten in C.

* tt/bisect-in-c:
  bisect--helper: `bisect_start` shell function partially in C
  bisect--helper: `get_terms` & `bisect_terms` shell function in C
  bisect--helper: `bisect_next_check` shell function in C
  bisect--helper: `check_and_set_terms` shell function in C
  wrapper: move is_empty_file() and rename it as is_empty_or_missing_file()
  bisect--helper: `bisect_write` shell function in C
  bisect--helper: `bisect_reset` shell function in C

A new encoding UTF-16LE-BOM has been invented to force encoding to
UTF-16 with BOM in little endian byte order, which cannot be directly
generated by using iconv.

* tb/utf-16-le-with-explicit-bom:
  Support working-tree-encoding "UTF-16LE-BOM"

"git cat-file --batch" reported a dangling symbolic link by
mistake, when it wanted to report that a given name is ambiguous.

* dt/cat-file-batch-ambiguous:
  t1512: test ambiguous cat-file --batch and --batch-output
  Do not print 'dangling' for cat-file in case of ambiguity

Docfix.

* km/init-doc-typofix:
  init docs: correct a punctuation typo

"git rebase --merge" as been reimplemented by reusing the internal
machinery used for "git rebase -i".

* en/rebase-merge-on-sequencer:
  rebase: implement --merge via the interactive machinery
  rebase: define linearization ordering and enforce it
  git-legacy-rebase: simplify unnecessary triply-nested if
  git-rebase, sequencer: extend --quiet option for the interactive machinery
  am, rebase--merge: do not overlook --skip'ed commits with post-rewrite
  t5407: add a test demonstrating how interactive handles --skip differently
  rebase: fix incompatible options error message
  rebase: make builtin and legacy script error messages the same

The getnanos() helper always gets the current time from our
getnanotime() facility. The caller cannot override it via TEST_DATE_NOW,
and hence we simply ignore the "now" parameter to the function. Let's
remove it, as it may mislead callers into thinking it does something.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

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

The commit-graph facility did not work when in-core objects that
are promoted from unknown type to commit (e.g. a commit that is
accessed via a tag that refers to it) were involved, which has been
corrected.

* sg/object-as-type-commit-graph-fix:
  object_as_type: initialize commit-graph-related fields of 'struct commit'

"git fetch" output cleanup.

* nd/fetch-compact-update:
  fetch: prefer suffix substitution in compact fetch.output

Cocci rule update.

* sg/strbuf-addbuf-cocci:
  strbuf.cocci: suggest strbuf_addbuf() to add one strbuf to an other

"git instaweb" learned to drive http.server that comes with
"batteries included" Python installation (both Python2 & 3).

* az/instaweb-py3-http-server:
  git-instaweb: add Python builtin http.server support

When GIT_SEQUENCE_EDITOR is set, the command was incorrectly
started when modes of "git rebase" that implicitly uses the
machinery for the interactive rebase are run, which has been
corrected.

* pw/no-editor-in-rebase-i-implicit:
  implicit interactive rebase: don't run sequence editor

"git diff --color-moved --cc --stat -p" did not work well due to
funny interaction between a bug in color-moved and the rest, which
has been fixed.

* jk/diff-cc-stat-fixes:
  combine-diff: treat --dirstat like --stat
  combine-diff: treat --summary like --stat
  combine-diff: treat --shortstat like --stat
  combine-diff: factor out stat-format mask
  diff: clear emitted_symbols flag after use
  t4006: resurrect commented-out tests

"git checkout -b <new> [HEAD]" to create a new branch from the
current commit and check it out ought to be a no-op in the index
and the working tree in normal cases, but there are corner cases
that do require updates to the index and the working tree.  Running
it immediately after "git clone --no-checkout" is one of these
cases that an earlier optimization kicked in incorrectly, which has
been fixed.

* bp/checkout-new-branch-optim:
  checkout: fix regression in checkout -b on intitial checkout
  checkout: add test demonstrating regression with checkout -b on initial commit

Doc typo/stylo fixes.

* ja/doc-style-fix:
  doc: tidy asciidoc style

"git pack-objects" incorrectly used uninitialized mutex, which has
been corrected.

* ph/pack-objects-mutex-fix:
  pack-objects: merge read_lock and lock in packing_data struct
  pack-objects: move read mutex to packing_data struct

Asking "git check-attr" about a macro (e.g. "binary") on a specific
path did not work correctly, even though "git check-attr -a" listed
such a macro correctly.  This has been corrected.

* jk/attr-macro-fix:
  attr: do not mark queried macros as unset

Test fix for Windows.

* js/test-git-installed:
  tests: explicitly use `test-tool.exe` on Windows

On a case-insensitive filesystem, we failed to compare the part of
the path that is above the worktree directory in an absolute
pathname, which has been corrected.

* js/abspath-part-inside-repo:
  abspath_part_inside_repo: respect core.ignoreCase

Fix namespace support in protocol v2.

* jt/namespaced-ls-refs-fix:
  ls-refs: filter refs using namespace-stripped name

The codepath to show progress meter while writing out commit-graph
file has been improved.

* ab/commit-graph-write-progress:
  commit-graph write: emit a percentage for all progress
  commit-graph write: add itermediate progress
  commit-graph write: remove empty line for readability
  commit-graph write: add more descriptive progress output
  commit-graph write: show progress for object search
  commit-graph write: more descriptive "writing out" output
  commit-graph write: add "Writing out" progress output
  commit-graph: don't call write_graph_chunk_extra_edges() unnecessarily
  commit-graph: rename "large edges" to "extra edges"

The codepath to write out commit-graph has been optimized by
following the usual pattern of visiting objects in in-pack order.

* ab/commit-graph-write-optim:
  commit-graph write: use pack order when finding commits

Test update.

* js/t6042-timing-fix:
  t6042: work around speed optimization on Windows

"git add --ignore-errors" did not work as advertised and instead
worked as an unintended synonym for "git add --renormalize", which
has been fixed.

* jk/add-ignore-errors-bit-assignment-fix:
  add: use separate ADD_CACHE_RENORMALIZE flag

In Git for Windows, "git clone \\server\share\path" etc. that uses
UNC paths from command line had bad interaction with its shell
emulation.

* js/mingw-unc-path-w-backslashes:
  mingw: special-case arguments to `sh`
  mingw (t5580): document bug when cloning from backslashed UNC paths

An obvious typo in an assertion error message has been fixed.

* cc/test-ref-store-typofix:
  helper/test-ref-store: fix "new-sha1" vs "old-sha1" typo

"git fetch" and "git upload-pack" learned to send all exchange over
the sideband channel while talking the v2 protocol.

* jt/fetch-v2-sideband:
  tests: define GIT_TEST_SIDEBAND_ALL
  {fetch,upload}-pack: sideband v2 fetch response
  sideband: reverse its dependency on pkt-line
  pkt-line: introduce struct packet_writer
  pack-protocol.txt: accept error packets in any context
  Use packet_reader instead of packet_read_line