Log Message:
Git 2.9 Release Notes
=====================

Backward compatibility notes
----------------------------

The end-user facing Porcelain level commands in the "git diff" and
"git log" family by default enable the rename detection; you can still
use "diff.renames" configuration variable to disable this.

Merging two branches that have no common ancestor with "git merge" is
by default forbidden now to prevent creating such an unusual merge by
mistake.

The output formats of "git log" that indents the commit log message by
4 spaces now expands HT in the log message by default.  You can use
the "--no-expand-tabs" option to disable this.

"git commit-tree" plumbing command required the user to always sign
its result when the user sets the commit.gpgsign configuration
variable, which was an ancient mistake, which this release corrects.
A script that drives commit-tree, if it relies on this mistake, now
needs to read commit.gpgsign and pass the -S option as necessary.

Updates since v2.8
------------------

UI, Workflows & Features

 * Comes with git-multimail 1.3.1 (in contrib/).

 * The end-user facing commands like "git diff" and "git log"
   now enable the rename detection by default.

 * The credential.helper configuration variable is cumulative and
   there is no good way to override it from the command line.  As
   a special case, giving an empty string as its value now serves
   as the signal to clear the values specified in various files.

 * A new "interactive.diffFilter" configuration can be used to
   customize the diff shown in "git add -i" sessions.

 * "git p4" now allows P4 author names to be mapped to Git author
   names.

 * "git rebase -x" can be used without passing "-i" option.

 * "git -c credential.<var>=<value> submodule" can now be \ 
used to
   propagate configuration variables related to credential helper
   down to the submodules.

 * "git tag" can create an annotated tag without explicitly given an
   "-a" (or "-s") option (i.e. when a tag message is given). \ 
 A new
   configuration variable, tag.forceSignAnnotated, can be used to tell
   the command to create signed tag in such a situation.

 * "git merge" used to allow merging two branches that have no common
   base by default, which led to a brand new history of an existing
   project created and then get pulled by an unsuspecting maintainer,
   which allowed an unnecessary parallel history merged into the
   existing project.  The command has been taught not to allow this by
   default, with an escape hatch "--allow-unrelated-histories" option
   to be used in a rare event that merges histories of two projects
   that started their lives independently.

 * "git pull" has been taught to pass the \ 
"--allow-unrelated-histories"
   option to underlying "git merge".

 * "git apply -v" learned to report paths in the patch that were
   skipped via --include/--exclude mechanism or being outside the
   current working directory.

 * Shell completion (in contrib/) updates.

 * The commit object name reported when "rebase -i" stops has been
   shortened.

 * "git worktree add" can be given "--no-checkout" option to only
   create an empty worktree without checking out the files.

 * "git mergetools" learned to drive ExamDiff.

 * "git pull --rebase" learned "--[no-]autostash" option, so that
   the rebase.autostash configuration variable set to true can be
   overridden from the command line.

 * When "git log" shows the log message indented by 4-spaces, the
   remainder of a line after a HT does not align in the way the author
   originally intended.  The command now expands tabs by default to help
   such a case, and allows the users to override it with a new option,
   "--no-expand-tabs".

 * "git send-email" now uses a more readable timestamps when
   formulating a message ID.

 * "git rerere" can encounter two or more files with the same conflict
   signature that have to be resolved in different ways, but there was
   no way to record these separate resolutions.

 * "git p4" learned to record P4 jobs in Git commit that imports from
   the history in Perforce.

 * "git describe --contains" often made a hard-to-justify choice of
   tag to name a given commit, because it tried to come up
   with a name with smallest number of hops from a tag, causing an old
   commit whose close descendant that is recently tagged were not
   described with respect to an old tag but with a newer tag.  It did
   not help that its computation of "hop" count was further tweaked to
   penalize being on a side branch of a merge.  The logic has been
   updated to favor using the tag with the oldest tagger date, which
   is a lot easier to explain to the end users: "We describe a commit
   in terms of the (chronologically) oldest tag that contains the
   commit."

 * "git clone" learned the "--shallow-submodules" option.

 * HTTP transport clients learned to throw extra HTTP headers at the
   server, specified via http.extraHeader configuration variable.

 * The "--compaction-heuristic" option to "git diff" family of
   commands enables a heuristic to make the patch output more readable
   by using a blank line as a strong hint that the contents before and
   after it belong to logically separate units.  It is still
   experimental.

 * A new configuration variable core.hooksPath allows customizing
   where the hook directory is.

 * An earlier addition of "sanitize_submodule_env" with 14111fc4 (git:
   submodule honor -c credential.* from command line, 2016-02-29)
   turned out to be a convoluted no-op; implement what it wanted to do
   correctly, and stop filtering settings given via "git -c var=val".

 * "git commit --dry-run" reported "No, no, you cannot \ 
commit." in one
   case where "git commit" would have allowed you to commit, and this
   improves it a little bit ("git commit --dry-run --short" still does
   not give you the correct answer, for example).  This is a stop-gap
   measure in that "commit --short --dry-run" still gives an incorrect
   result.

 * The experimental "multiple worktree" feature gains more safety to
   forbid operations on a branch that is checked out or being actively
   worked on elsewhere, by noticing that e.g. it is being rebased.

 * "git format-patch" learned a new "--base" option to \ 
record what
   (public, well-known) commit the original series was built on in
   its output.

 * "git commit" learned to pay attention to the "commit.verbose"
   configuration variable and act as if the "--verbose" option
   was given from the command line.

 * Updated documentation gives hints to GMail users with two-factor
   auth enabled that they need app-specific-password when using
   "git send-email".

 * The manpage output of our documentation did not render well in
   terminal; typeset literals in bold by default to make them stand
   out more.

 * The mark-up in the top-level README.md file has been updated to
   typeset CLI command names differently from the body text.

Performance, Internal Implementation, Development Support etc.

 * The embedded args argv-array in the child process is used to build
   the command line to run pack-objects instead of using a separate
   array of strings.

 * A test for tags has been restructured so that more parts of it can
   easily be run on a platform without a working GnuPG.

 * The startup_info data, which records if we are working inside a
   repository (among other things), are now uniformly available to Git
   subcommand implementations, and Git avoids attempting to touch
   references when we are not in a repository.

 * The command line argument parser for "receive-pack" has been
   rewritten to use parse-options.

 * A major part of "git submodule update" has been ported to C to take
   advantage of the recently added framework to run download tasks in
   parallel.  Other updates to "git submodule" that move pieces of
   logic to C continues.

 * Rename bunch of tests on "git clone" for better organization.

 * The tests that involve running httpd leaked the system-wide
   configuration in /etc/gitconfig to the tested environment.

 * Build updates for MSVC.

 * The repository set-up sequence has been streamlined (the biggest
   change is that there is no longer git_config_early()), so that we
   do not attempt to look into refs/* when we know we do not have a
   Git repository.

 * Code restructuring around the "refs" API to prepare for pluggable
   refs backends.

 * Sources to many test helper binaries and the generated helpers
   have been moved to t/helper/ subdirectory to reduce clutter at the
   top level of the tree.

 * Unify internal logic between "git tag -v" and "git verify-tag"
   commands by making one directly call into the other.

 * "merge-recursive" strategy incorrectly checked if a path that is
   involved in its internal merge exists in the working tree.

 * The test scripts for "git p4" (but not "git p4" implementation
   itself) has been updated so that they would work even on a system
   where the installed version of Python is python 3.

 * As nobody maintains our in-tree git.spec.in and distros use their
   own spec file, we stopped pretending that we support "make rpm".

 * Move from "unsigned char[20]" to "struct object_id" continues.

 * The code for warning_errno/die_errno has been refactored and a new
   error_errno() reporting helper is introduced.
   (merge 1da045f nd/error-errno later to maint).

 * Running tests with '-x' option to trace the individual command
   executions is a useful way to debug test scripts, but some tests
   that capture the standard error stream and check what the command
   said can be broken with the trace output mixed in.  When running
   our tests under "bash", however, we can redirect the trace output
   to another file descriptor to keep the standard error of programs
   being tested intact.

 * t0040 had too many unnecessary repetitions in its test data.  Teach
   test-parse-options program so that a caller can tell what it
   expects in its output, so that these repetitions can be cleaned up.

 * Add perf test for "rebase -i".

 * Common mistakes when writing gitlink: in our documentation are
   found by "make check-docs".

 * t9xxx series has been updated primarily for readability, while
   fixing small bugs in it.  A few scripted Porcelain commands have
   also been updated to fix possible bugs around their use of
   "test -z" and "test -n".

 * CI test was taught to run git-svn tests.

 * "git cat-file --batch-all" has been sped up, by taking advantage
   of the fact that it does not have to read a list of objects, in two
   ways.

 * test updates to make it more readable and maintainable.
   (merge e6273f4 es/t1500-modernize later to maint).

 * "make DEVELOPER=1" worked as expected; setting DEVELOPER=1 in
   config.mak didn't.
   (merge 51dd3e8 mm/makefile-developer-can-be-in-config-mak later to maint).

 * The way how "submodule--helper list" signals unmatch error to its
   callers has been updated.

 * A bash-ism "local" has been removed from "git submodule" \ 
scripted
   Porcelain.

Also contains various documentation updates and code clean-ups.