Log Message:
Git 2.11 Release Notes
======================

Backward compatibility notes.

 * An empty string used as a pathspec element has always meant
   'everything matches', but it is too easy to write a script that
   finds a path to remove in $path and run 'git rm "$paht"' by
   mistake (when the user meant to give "$path"), which ends up
   removing everything.  This release starts warning about the
   use of an empty string that is used for 'everything matches' and
   asks users to use a more explicit '.' for that instead.

   The hope is that existing users will not mind this change, and
   eventually the warning can be turned into a hard error, upgrading
   the deprecation into removal of this (mis)feature.

 * The historical argument order "git merge <msg> HEAD \ 
<commit>..."
   has been deprecated for quite some time, and will be removed in the
   next release (not this one).

 * The default abbreviation length, which has historically been 7, now
   scales as the repository grows, using the approximate number of
   objects in the repository and a bit of math around the birthday
   paradox.  The logic suggests to use 12 hexdigits for the Linux
   kernel, and 9 to 10 for Git itself.

Updates since v2.10
-------------------

UI, Workflows & Features

 * Comes with new version of git-gui, now at its 0.21.0 tag.

 * "git format-patch --cover-letter HEAD^" to format a single patch
   with a separate cover letter now numbers the output as [PATCH 0/1]
   and [PATCH 1/1] by default.

 * An incoming "git push" that attempts to push too many bytes can now
   be rejected by setting a new configuration variable at the receiving
   end.

 * "git nosuchcommand --help" said "No manual entry for \ 
gitnosuchcommand",
   which was not intuitive, given that "git nosuchcommand" said "git:
   'nosuchcommand' is not a git command".

 * "git clone --recurse-submodules --reference $path $URL" is a way to
   reduce network transfer cost by borrowing objects in an existing
   $path repository when cloning the superproject from $URL; it
   learned to also peek into $path for presence of corresponding
   repositories of submodules and borrow objects from there when able.

 * The "git diff --submodule={short,log}" mechanism has been enhanced
   to allow "--submodule=diff" to show the patch between the submodule
   commits bound to the superproject.

 * Even though "git hash-objects", which is a tool to take an
   on-filesystem data stream and put it into the Git object store,
   can perform "outside-world-to-Git" conversions (e.g.
   end-of-line conversions and application of the clean-filter), and
   it has had this feature on by default from very early days, its reverse
   operation "git cat-file", which takes an object from the Git object
   store and externalizes it for consumption by the outside world,
   lacked an equivalent mechanism to run the "Git-to-outside-world"
   conversion.  The command learned the "--filters" option to do so.

 * Output from "git diff" can be made easier to read by intelligently \ 
selecting
   which lines are common and which lines are added/deleted
   when the lines before and after the changed section
   are the same.  A command line option (--indent-heuristic) and a
   configuration variable (diff.indentHeuristic) are added to help with the
   experiment to find good heuristics.

 * In some projects, it is common to use "[RFC PATCH]" as the subject
   prefix for a patch meant for discussion rather than application.  A
   new format-patch option "--rfc" is a short-hand for \ 
"--subject-prefix=RFC PATCH"
   to help the participants of such projects.

 * "git add --chmod={+,-}x <pathspec>" only changed the
   executable bit for paths that are either new or modified. This has
   been corrected to change the executable bit for all paths that match
   the given pathspec.

 * When "git format-patch --stdout" output is placed as an in-body
   header and it uses RFC2822 header folding, "git am" fails to
   put the header line back into a single logical line.  The
   underlying "git mailinfo" was taught to handle this properly.

 * "gitweb" can spawn "highlight" to show blob contents with
   (programming) language-specific syntax highlighting, but only
   when the language is known.  "highlight" can however be told
   to guess the language itself by giving it "--force" option, which
   has been enabled.

 * "git gui" l10n to Portuguese.

 * When given an abbreviated object name that is not (or more
   realistically, "no longer") unique, we gave a fatal error
   "ambiguous argument".  This error is now accompanied by a hint that
   lists the objects beginning with the given prefix.  During the
   course of development of this new feature, numerous minor bugs were
   uncovered and corrected, the most notable one of which is that we
   gave "short SHA1 xxxx is ambiguous." twice without good reason.

 * "git log rev^..rev" is an often-used revision range specification
   to show what was done on a side branch merged at rev.  This has
   gained a short-hand "rev^-1".  In general "rev^-$n" is \ 
the same as
   "^rev^$n rev", i.e. what has happened on other branches while the
   history leading to nth parent was looking the other way.

 * In recent versions of cURL, GSSAPI credential delegation is
   disabled by default due to CVE-2011-2192; introduce a http.delegation
   configuration variable to selectively allow enabling this.
   (merge 26a7b23429 ps/http-gssapi-cred-delegation later to maint).

 * "git mergetool" learned to honor "-O<orderfile>" to \ 
control the
   order of paths to present to the end user.

 * "git diff/log --ws-error-highlight=<kind>" lacked the \ 
corresponding
   configuration variable (diff.wsErrorHighlight) to set it by default.

 * "git ls-files" learned the "--recurse-submodules" option
   to get a listing of tracked files across submodules (i.e. this
   only works with the "--cached" option, not for listing untracked or
   ignored files).  This would be a useful tool to sit on the upstream
   side of a pipe that is read with xargs to work on all working tree
   files from the top-level superproject.

 * A new credential helper that talks via "libsecret" with
   implementations of XDG Secret Service API has been added to
   contrib/credential/.

 * The GPG verification status shown by the "%G?" pretty format specifier
   was not rich enough to differentiate a signature made by an expired
   key, a signature made by a revoked key, etc.  New output letters
   have been assigned to express them.

 * In addition to purely abbreviated commit object names, "gitweb"
   learned to turn "git describe" output (e.g. v2.9.3-599-g2376d31787)
   into clickable links in its output.

 * "git commit" created an empty commit when invoked with an index
   consisting solely of intend-to-add paths (added with "git add -N").
   It now requires the "--allow-empty" option to create such a commit.
   The same logic prevented "git status" from showing such paths as \ 
"new files" in the
   "Changes not staged for commit" section.

 * The smudge/clean filter API spawns an external process
   to filter the contents of each path that has a filter defined.  A
   new type of "process" filter API has been added to allow the first
   request to run the filter for a path to spawn a single process, and
   all filtering is served by this single process for multiple
   paths, reducing the process creation overhead.

 * The user always has to say "stash@{$N}" when naming a single
   element in the default location of the stash, i.e. reflogs in
   refs/stash.  The "git stash" command learned to accept "git stash
   apply 4" as a short-hand for "git stash apply stash@{4}".

Performance, Internal Implementation, Development Support etc.

 * The delta-base-cache mechanism has been a key to the performance in
   a repository with a tightly packed packfile, but it did not scale
   well even with a larger value of core.deltaBaseCacheLimit.

 * Enhance "git status --porcelain" output by collecting more data on
   the state of the index and the working tree files, which may
   further be used to teach git-prompt (in contrib/) to make fewer
   calls to git.

 * Extract a small helper out of the function that reads the authors
   script file "git am" internally uses.
   (merge a77598e jc/am-read-author-file later to maint).

 * Lift calls to exit(2) and die() higher in the callchain in
   sequencer.c files so that more helper functions in it can be used
   by callers that want to handle error conditions themselves.

 * "git am" has been taught to make an internal call to "git \ 
apply"'s
   innards without spawning the latter as a separate process.

 * The ref-store abstraction was introduced to the refs API so that we
   can plug in different backends to store references.

 * The "unsigned char sha1[20]" to "struct object_id" conversion
   continues.  Notable changes in this round includes that ce->sha1,
   i.e. the object name recorded in the cache_entry, turns into an
   object_id.

 * JGit can show a fake ref "capabilities^{}" to "git fetch" \ 
when it
   does not advertise any refs, but "git fetch" was not prepared to
   see such an advertisement.  When the other side disconnects without
   giving any ref advertisement, we used to say "there may not be a
   repository at that URL", but we may have seen other advertisements
   like "shallow" and ".have" in which case we definitely \ 
know that a
   repository is there.  The code to detect this case has also been
   updated.

 * Some codepaths in "git pack-objects" were not ready to use an
   existing pack bitmap; now they are and as a result they have
   become faster.

 * The codepath in "git fsck" to detect malformed tree objects has
   been updated not to die but keep going after detecting them.

 * We call "qsort(array, nelem, sizeof(array[0]), fn)", and most of
   the time third parameter is redundant.  A new QSORT() macro lets us
   omit it.

 * "git pack-objects" in a repository with many packfiles used to
   spend a lot of time looking for/at objects in them; the accesses to
   the packfiles are now optimized by checking the most-recently-used
   packfile first.
   (merge c9af708b1a jk/pack-objects-optim-mru later to maint).

 * Codepaths involved in interacting alternate object stores have
   been cleaned up.

 * In order for the receiving end of "git push" to inspect the
   received history and decide to reject the push, the objects sent
   from the sending end need to be made available to the hook and
   the mechanism for the connectivity check, and this was done
   traditionally by storing the objects in the receiving repository
   and letting "git gc" expire them.  Instead, store the newly
   received objects in a temporary area, and make them available by
   reusing the alternate object store mechanism to them only while we
   decide if we accept the check, and once we decide, either migrate
   them to the repository or purge them immediately.

 * The require_clean_work_tree() helper was recreated in C when "git
   pull" was rewritten from shell; the helper is now made available to
   other callers in preparation for upcoming "rebase -i" work.

 * "git upload-pack" had its code cleaned-up and performance improved
   by reducing use of timestamp-ordered commit-list, which was
   replaced with a priority queue.

 * "git diff --no-index" codepath has been updated not to try to peek
   into a .git/ directory that happens to be under the current
   directory, when we know we are operating outside any repository.

 * Update of the sequencer codebase to make it reusable to reimplement
   "rebase -i" continues.

 * Git generally does not explicitly close file descriptors that were
   open in the parent process when spawning a child process, but most
   of the time the child does not want to access them. As Windows does
   not allow removing or renaming a file that has a file descriptor
   open, a slow-to-exit child can even break the parent process by
   holding onto them.  Use O_CLOEXEC flag to open files in various
   codepaths.

 * Update "interpret-trailers" machinery and teach it that people in
   the real world write all sorts of cruft in the "trailer" that was
   originally designed to have the neat-o "Mail-Header: like thing"
   and nothing else.