Git 2.16 Release Notes
======================

Backward compatibility notes and other notable changes.

 * Use of an empty string as a pathspec element that is used for
   'everything matches' is now an error.


Updates since v2.15
-------------------

UI, Workflows & Features

 * An empty string as a pathspec element that means "everything"
   i.e. 'git add ""', is now illegal.  We started this by first
   deprecating and warning a pathspec that has such an element in
   2.11 (Nov 2016).

 * A hook script that is set unexecutable is simply ignored.  Git
   notifies when such a file is ignored, unless the message is
   squelched via advice.ignoredHook configuration.

 * "git pull" has been taught to accept "--[no-]signoff" option and
   pass it down to "git merge".

 * The "--push-option=<string>" option to "git push" now defaults to a
   list of strings configured via push.pushOption variable.

 * "gitweb" checks if a directory is searchable with Perl's "-x"
   operator, which can be enhanced by using "filetest 'access'"
   pragma, which now we do.

 * "git stash save" has been deprecated in favour of "git stash push".

 * The set of paths output from "git status --ignored" was tied
   closely with its "--untracked=<mode>" option, but now it can be
   controlled more flexibly.  Most notably, a directory that is
   ignored because it is listed to be ignored in the ignore/exclude
   mechanism can be handled differently from a directory that ends up
   to be ignored only because all files in it are ignored.

 * The remote-helper for talking to MediaWiki has been updated to
   truncate an overlong pagename so that ".mw" suffix can still be
   added.

 * The remote-helper for talking to MediaWiki has been updated to
   work with mediawiki namespaces.

 * The "--format=..." option "git for-each-ref" takes learned to show
   the name of the 'remote' repository and the ref at the remote side
   that is affected for 'upstream' and 'push' via "%(push:remotename)"
   and friends.

 * Doc and message updates to teach users "bisect view" is a synonym
   for "bisect visualize".

 * "git bisect run" that did not specify any command to run used to go
   ahead and treated all commits to be tested as 'good'.  This has
   been corrected by making the command error out.

 * The SubmittingPatches document has been converted to produce an
   HTML version via AsciiDoc/Asciidoctor.

 * We learned to talk to watchman to speed up "git status" and other
   operations that need to see which paths have been modified.

 * The "diff" family of commands learned to ignore differences in
   carriage return at the end of line.

 * Places that know about "sendemail.to", like documentation and shell
   completion (in contrib/) have been taught about "sendemail.tocmd",
   too.

 * "git add --renormalize ." is a new and safer way to record the fact
   that you are correcting the end-of-line convention and other
   "convert_to_git()" glitches in the in-repository data.

 * "git branch" and "git checkout -b" are now forbidden from creating
   a branch whose name is "HEAD".

 * "git branch --list" learned to show its output through the pager by
   default when the output is going to a terminal, which is controlled
   by the pager.branch configuration variable.  This is similar to a
   recent change to "git tag --list".

 * "git grep -W", "git diff -W" and their friends learned a heuristic
   to extend a pre-context beyond the line that matches the "function
   pattern" (aka "diff.*.xfuncname") to include a comment block, if
   exists, that immediately precedes it.

 * "git config --expiry-date gc.reflogexpire" can read "2.weeks" from
   the configuration and report it as a timestamp, just like "--int"
   would read "1k" and report 1024, to help consumption by scripts.

 * The shell completion (in contrib/) learned that "git pull" can take
   the "--autostash" option.

 * The tagnames "git log --decorate" uses to annotate the commits can
   now be limited to subset of available refs with the two additional
   options, --decorate-refs[-exclude]=<pattern>.

 * "git grep" compiled with libpcre2 sometimes triggered a segfault,
   which is being fixed.

 * "git send-email" tries to see if the sendmail program is available
   in /usr/lib and /usr/sbin; extend the list of locations to be
   checked to also include directories on $PATH.

 * "git diff" learned, "--anchored", a variant of the "--patience"
   algorithm, to which the user can specify which 'unique' line to be
   used as anchoring points.

 * The way "git worktree add" determines what branch to create from
   where and checkout in the new worktree has been updated a bit.

 * Ancient part of codebase still shows dots after an abbreviated
   object name just to show that it is not a full object name, but
   these ellipses are confusing to people who newly discovered Git
   who are used to seeing abbreviated object names and find them
   confusing with the range syntax.


Performance, Internal Implementation, Development Support etc.

 * An earlier update made it possible to use an on-stack in-core
   lockfile structure (as opposed to having to deliberately leak an
   on-heap one).  Many codepaths have been updated to take advantage
   of this new facility.

 * Calling cmd_foo() as if it is a general purpose helper function is
   a no-no.  Correct two instances of such to set an example.

 * We try to see if somebody runs our test suite with a shell that
   does not support "local" like bash/dash does.

 * An early part of piece-by-piece rewrite of "git bisect" in C.

 * GSoC to piece-by-piece rewrite "git submodule" in C.

 * Optimize the code to find shortest unique prefix of object names.

 * Pathspec-limited revision traversal was taught not to keep finding
   unneeded differences once it knows two trees are different inside
   given pathspec.

 * Conversion from uchar[20] to struct object_id continues.

 * Code cleanup.

 * A single-word "unsigned flags" in the diff options is being split
   into a structure with many bitfields.

 * TravisCI build updates.

 * Parts of a test to drive the long-running content filter interface
   has been split into its own module, hopefully to eventually become
   reusable.

 * Drop (perhaps overly cautious) sanity check before using the index
   read from the filesystem at runtime.

 * The build procedure has been taught to avoid some unnecessary
   instability in the build products.

 * A new mechanism to upgrade the wire protocol in place is proposed
   and demonstrated that it works with the older versions of Git
   without harming them.

 * An infrastructure to define what hash function is used in Git is
   introduced, and an effort to plumb that throughout various
   codepaths has been started.

 * The code to iterate over loose object files got optimized.

 * An internal function that was left for backward compatibility has
   been removed, as there is no remaining callers.

 * Historically, the diff machinery for rename detection had a
   hardcoded limit of 32k paths; this is being lifted to allow users
   trade cycles with a (possibly) easier to read result.

 * The tracing infrastructure has been optimized for cases where no
   tracing is requested.

Also contains various documentation updates and code clean-ups.


Fixes since v2.15
-----------------

 * "auto" as a value for the columnar output configuration ought to
   judge "is the output consumed by humans?" with the same criteria as
   "auto" for coloured output configuration, i.e. either the standard
   output stream is going to tty, or a pager is in use.  We forgot the
   latter, which has been fixed.

 * The experimental "color moved lines differently in diff output"
   feature was buggy around "ignore whitespace changes" edges, which
   has been corrected.

 * Instead of using custom line comparison and hashing functions to
   implement "moved lines" coloring in the diff output, use the pair
   of these functions from lower-layer xdiff/ code.

 * Some codepaths did not check for errors when asking what branch the
   HEAD points at, which have been fixed.

 * "git commit", after making a commit, did not check for errors when
   asking on what branch it made the commit, which has been corrected.

 * "git status --ignored -u" did not stop at a working tree of a
   separate project that is embedded in an ignored directory and
   listed files in that other project, instead of just showing the
   directory itself as ignored.

 * A broken access to object databases in recent update to "git grep
   --recurse-submodules" has been fixed.

 * A recent regression in "git rebase -i" that broke execution of git
   commands from subdirectories via "exec" instruction has been fixed.

 * A (possibly flakey) test fix.

 * "git check-ref-format --branch @{-1}" bit a "BUG()" when run
   outside a repository for obvious reasons; clarify the documentation
   and make sure we do not even try to expand the at-mark magic in
   such a case, but still call the validation logic for branch names.

 * "git fetch --recurse-submodules" now knows that submodules can be
   moved around in the superproject in addition to getting updated,
   and finds the ones that need to be fetched accordingly.

 * Command line completion (in contrib/) update.

 * Description of blame.{showroot,blankboundary,showemail,date}
   configuration variables have been added to "git config --help".

 * After an error from lstat(), diff_populate_filespec() function
   sometimes still went ahead and used invalid data in struct stat,
   which has been fixed.

 * UNC paths are also relevant in Cygwin builds and they are now
   tested just like Mingw builds.

 * Correct start-up sequence so that a repository could be placed
   immediately under the root directory again (which was broken at
   around Git 2.13).

 * The credential helper for libsecret (in contrib/) has been improved
   to allow possibly prompting the end user to unlock secrets that are
   currently locked (otherwise the secrets may not be loaded).

 * MinGW updates.

 * Error checking in "git imap-send" for empty response has been
   improved.

 * Recent update to the refs infrastructure implementation started
   rewriting packed-refs file more often than before; this has been
   optimized again for most trivial cases.

 * Some error messages did not quote filenames shown in it, which have
   been fixed.

 * "git rebase -i" recently started misbehaving when a submodule that
   is configured with 'submodule.<name>.ignore' is dirty; this has
   been corrected.

 * Building with NO_LIBPCRE1_JIT did not disable it, which has been fixed.

 * We used to add an empty alternate object database to the system
   that does not help anything; it has been corrected.

 * Doc update around use of "format-patch --subject-prefix" etc.

 * A fix for an ancient bug in "git apply --ignore-space-change" codepath.

 * Clarify and enhance documentation for "merge-base --fork-point", as
   it was clear what it computed but not why/what for.

 * A few scripts (both in production and tests) incorrectly redirected
   their error output.  These have been corrected.

 * "git notes" sent its error message to its standard output stream,
   which was corrected.

 * The three-way merge performed by "git cherry-pick" was confused
   when a new submodule was added in the meantime, which has been
   fixed (or "papered over").

 * The sequencer machinery (used by "git cherry-pick A..B", and "git
   rebase -i", among other things) would have lost a commit if stopped
   due to an unlockable index file, which has been fixed.

 * "git apply --inaccurate-eof" when used with "--ignore-space-change"
   triggered an internal sanity check, which has been fixed.

 * Command line completion (in contrib/) has been taught about the
   "--copy" option of "git branch".

 * When "git rebase" prepared an mailbox of changes and fed it to "git
   am" to replay them, it was confused when a stray "From " happened
   to be in the log message of one of the replayed changes.  This has
   been corrected.

 * There was a recent semantic mismerge in the codepath to write out a
   section of a configuration section, which has been corrected.

 * Mentions of "git-rebase" and "git-am" (dashed form) still remained
   in end-user visible strings emitted by the "git rebase" command;
   they have been corrected.

 * Contrary to the documentation, "git pull -4/-6 other-args" did not
   ask the underlying "git fetch" to go over IPv4/IPv6, which has been
   corrected.

 * "git checkout --recursive" may overwrite and rewind the history of
   the branch that happens to be checked out in submodule
   repositories, which might not be desirable.  Detach the HEAD but
   still allow the recursive checkout to succeed in such a case.
   (merge 57f22bf997 sb/submodule-recursive-checkout-detach-head later to maint).

 * "git branch --set-upstream" has been deprecated and (sort of)
   removed, as "--set-upstream-to" is the preferred one these days.
   The documentation still had "--set-upstream" listed on its
   synopsis section, which has been corrected.
   (merge a060f3d3d8 tz/branch-doc-remove-set-upstream later to maint).

 * Internally we use 0{40} as a placeholder object name to signal the
   codepath that there is no such object (e.g. the fast-forward check
   while "git fetch" stores a new remote-tracking ref says "we know
   there is no 'old' thing pointed at by the ref, as we are creating
   it anew" by passing 0{40} for the 'old' side), and expect that a
   codepath to locate an in-core object to return NULL as a sign that
   the object does not exist.  A look-up for an object that does not
   exist however is quite costly with a repository with large number
   of packfiles.  This access pattern has been optimized.
   (merge 87b5e236a1 jk/fewer-pack-rescan later to maint).

 * In addition to "git stash -m message", the command learned to
   accept "git stash -mmessage" form.
   (merge 5675473fcb ph/stash-save-m-option-fix later to maint).

 * @{-N} in "git checkout @{-N}" may refer to a detached HEAD state,
   but the documentation was not clear about it, which has been fixed.
   (merge 75ce149575 ks/doc-checkout-previous later to maint).

 * A regression in the progress eye-candy was fixed.
   (merge 9c5951cacf jk/progress-delay-fix later to maint).

 * The code internal to the recursive merge strategy was not fully
   prepared to see a path that is renamed to try overwriting another
   path that is only different in case on case insensitive systems.
   This does not matter in the current code, but will start to matter
   once the rename detection logic starts taking hints from nearby
   paths moving to some directory and moves a new path along with them.
   (merge 4cba2b0108 en/merge-recursive-icase-removal later to maint).

 * An v2.12-era regression in pathspec match logic, which made it look
   into submodule tree even when it is not desired, has been fixed.
   (merge eef3df5a93 bw/pathspec-match-submodule-boundary later to maint).

 * Amending commits in git-gui broke the author name that is non-ascii
   due to incorrect enconding conversion.

 * Recent update to the submodule configuration code broke "diff-tree"
   by accidentally stopping to read from the index upfront.
   (merge fd66bcc31f bw/submodule-config-cleanup later to maint).

 * Git shows a message to tell the user that it is waiting for the
   user to finish editing when spawning an editor, in case the editor
   opens to a hidden window or somewhere obscure and the user gets
   lost.
   (merge abfb04d0c7 ls/editor-waiting-message later to maint).

 * Other minor doc, test and build updates and code cleanups.
   (merge 1a1fc2d5b5 rd/man-prune-progress later to maint).
   (merge 0ba014035a rd/man-reflog-add-n later to maint).
   (merge e54b63359f rd/doc-notes-prune-fix later to maint).
   (merge ff4c9b413a sp/doc-info-attributes later to maint).
   (merge 7db2cbf4f1 jc/receive-pack-hook-doc later to maint).
   (merge 5a0526264b tg/t-readme-updates later to maint).
   (merge 5e83cca0b8 jk/no-optional-locks later to maint).
   (merge 826c778f7c js/hashmap-update-sample later to maint).
   (merge 176b2d328c sg/setup-doc-update later to maint).