Git 2.9 Release Notes
=====================

Backward compatibility note
---------------------------

The end-user facing Porcelain level commands in the "git diff" and
"git log" by default enables 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.


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

UI, Workflows & Features

 * The end-user facing Porcelain level commands like "diff" and "log"
   now enables 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" session.

 * "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 --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 in
   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.
   (merge 890fca8 jc/rerere-multi later to maint).

 * "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 give name to 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."
   (merge 7550424 js/name-rev-use-oldest-ref later to maint).

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

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

 * Patch output from "git diff" and friends has been tweaked to be
   more readable by using a blank line as a strong hint that the
   contents before and after it belong to a logically separate unit.


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.

 * 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" area 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.

   Note that this can break your tests if you check out revisions
   across the merge boundary of this topic, e0b58519 (Merge branch
   'nd/test-helpers', 2016-04-29), as bin-wrappers/test-* are not
   rebuilt to point the underlying executables.  For now, "make
   distclean" is your friend.

 * Unify internal logic between "git tag -v" and "git verify-tag"
   commands by making one directly call into the other.
   (merge bef234b st/verify-tag later to maint).

 * "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.
   (merge 1fb3fb4 ld/p4-test-py3 later to maint).

 * 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.


Also contains various documentation updates and code clean-ups.


Fixes since v2.8
----------------

Unless otherwise noted, all the fixes since v2.8 in the maintenance
track are contained in this release (see the maintenance releases'
notes for details).

 * "git config --get-urlmatch", unlike other variants of the "git
   config --get" family, did not signal error with its exit status
   when there was no matching configuration.

 * The "--local-env-vars" and "--resolve-git-dir" options of "git
   rev-parse" failed to work outside a repository when the command's
   option parsing was rewritten in 1.8.5 era.

 * "git index-pack --keep[=<msg>] pack-$name.pack" simply did not work.

 * Fetching of history by naming a commit object name directly didn't
   work across remote-curl transport.

 * A small memory leak in an error codepath has been plugged in xdiff
   code.

 * strbuf_getwholeline() did not NUL-terminate the buffer on certain
   corner cases in its error codepath.

 * "git mergetool" did not work well with conflicts that both sides
   deleted.

 * "git send-email" had trouble parsing alias file in mailrc format
   when lines in it had trailing whitespaces on them.

 * When "git merge --squash" stopped due to conflict, the concluding
   "git commit" failed to read in the SQUASH_MSG that shows the log
   messages from all the squashed commits.

 * "git merge FETCH_HEAD" dereferenced NULL pointer when merging
   nothing into an unborn history (which is arguably unusual usage,
   which perhaps was the reason why nobody noticed it).

 * When "git worktree" feature is in use, "git branch -d" allowed
   deletion of a branch that is checked out in another worktree,
   which was wrong.

 * When "git worktree" feature is in use, "git branch -m" renamed a
   branch that is checked out in another worktree without adjusting
   the HEAD symbolic ref for the worktree.

 * "git diff -M" used to work better when two originally identical
   files A and B got renamed to X/A and X/B by pairing A to X/A and B
   to X/B, but this was broken in the 2.0 timeframe.

 * "git send-pack --all <there>" was broken when its command line
   option parsing was written in the 2.6 timeframe.

 * "git format-patch --help" showed `-s` and `--no-patch` as if these
   are valid options to the command.  We already hide `--patch` option
   from the documentation, because format-patch is about showing the
   diff, and the documentation now hides these options as well.

 * When running "git blame $path" with unnormalized data in the index
   for the path, the data in the working tree was blamed, even though
   "git add" would not have changed what is already in the index, due
   to "safe crlf" that disables the line-end conversion.  It has been
   corrected.

 * A change back in version 2.7 to "git branch" broke display of a
   symbolic ref in a non-standard place in the refs/ hierarchy (we
   expect symbolic refs to appear in refs/remotes/*/HEAD to point at
   the primary branch the remote has, and as .git/HEAD to point at the
   branch we locally checked out).

 * A partial rewrite of "git submodule" in the 2.7 timeframe changed
   the way the gitdir: pointer in the submodules point at the real
   repository location to use absolute paths by accident.  This has
   been corrected.

 * "git commit" misbehaved in a few minor ways when an empty message
   is given via -m '', all of which has been corrected.

 * Support for CRAM-MD5 authentication method in "git imap-send" did
   not work well.

 * Upcoming OpenSSL 1.1.0 will break compilation b updating a few APIs
   we use in imap-send, which has been adjusted for the change.
   (merge 1245c74 ky/imap-send-openssl-1.1.0 later to maint).

 * The socks5:// proxy support added back in 2.6.4 days was not aware
   that socks5h:// proxies behave differently.

 * "git config" had a codepath that tried to pass a NULL to
   printf("%s"), which nobody seems to have noticed.

 * On Cygwin, object creation uses the "create a temporary and then
   rename it to the final name" pattern, not "create a temporary,
   hardlink it to the final name and then unlink the temporary"
   pattern.

   This is necessary to use Git on Windows shared directories, and is
   already enabled for the MinGW and plain Windows builds.  It also
   has been used in Cygwin packaged versions of Git for quite a while.
   See http://thread.gmane.org/gmane.comp.version-control.git/291853

 * "merge-octopus" strategy did not ensure that the index is clean
   when merge begins.

 * When "git merge" notices that the merge can be resolved purely at
   the tree level (without having to merge blobs) and the resulting
   tree happens to already exist in the object store, it forgot to
   update the index, which lead to an inconsistent state for later
   operations.

 * "git submodule" reports the paths of submodules the command
   recurses into, but this was incorrect when the command was not run
   from the root level of the superproject.
   (merge 2ab5660 sb/submodule-path-misc-bugs later to maint).

 * The "user.useConfigOnly" configuration variable makes it an error
   if users do not explicitly set user.name and user.email.  However,
   its check was not done early enough and allowed another error to
   trigger, reporting that the default value we guessed from the
   system setting was unusable.  This was a suboptimal end-user
   experience as we want the users to set user.name/user.email without
   relying on the auto-detection at all.
   (merge d3c06c1 da/user-useconfigonly later to maint).

 * "git mv old new" did not adjust the path for a submodule that lives
   as a subdirectory inside old/ directory correctly.
   (merge a127331 sb/mv-submodule-fix later to maint).

 * "git replace -e" did not honour "core.editor" configuration.
   (merge 36b1437 js/replace-edit-use-editor-configuration later to maint).

 * "git push" from a corrupt repository that attempts to push a large
   number of refs deadlocked; the thread to relay rejection notices
   for these ref updates blocked on writing them to the main thread,
   after the main thread at the receiving end notices that the push
   failed and decides not to read these notices and return a failure.
   (merge f924b52a jk/push-client-deadlock-fix later to maint).

 * mmap emulation on Windows has been optimized and work better without
   consuming paging store when not needed.
   (merge d5425d1 js/win32-mmap later to maint).

 * A question by "git send-email" to ask the identity of the sender
   has been updated.
   (merge 0d6b21e jd/send-email-to-whom later to maint).

 * UI consistency improvements for "git mergetool".
   (merge cce076e nf/mergetool-prompt later to maint).

 * "git rebase -m" could be asked to rebase an entire branch starting
   from the root, but failed by assuming that there always is a parent
   commit to the first commit on the branch.
   (merge 79f4344 bw/rebase-merge-entire-branch later to maint).

 * Fix a broken "p4 lfs" test.
   (merge 9e220fe ls/p4-lfs-test-fix-2.7.0 later to maint).

 * Recent update to Git LFS broke "git p4" by changing the output from
   its "lfs pointer" subcommand.
   (merge 82f2567 ls/p4-lfs later to maint).

 * "git fetch" test t5510 was flaky while running a (forced) automagic
   garbage collection.
   (merge bb05510 js/close-packs-before-gc later to maint).

 * Documentation updates to help contributors setting up Travis CI
   test for their patches.
   (merge 0e5d028 ls/travis-submitting-patches later to maint).

 * Some multi-byte encoding can have a backslash byte as a later part
   of one letter, which would confuse "highlight" filter used in
   gitweb.
   (merge 029f372 sk/gitweb-highlight-encoding later to maint).

 * Other minor clean-ups and documentation updates
   (merge 8b5a3e9 kn/for-each-tag-branch later to maint).
   (merge 99dab16 sb/misc-cleanups later to maint).
   (merge 7a6a44c cc/apply later to maint).
   (merge 6594883 nd/remove-unused later to maint).
   (merge 0ff7410 sg/test-lib-simplify-expr-away later to maint).
   (merge 060e776 jk/fix-attribute-macro-in-2.5 later to maint).
   (merge d16df0c rt/string-list-lookup-cleanup later to maint).
   (merge 376eb60 sb/config-exit-status-list later to maint).
   (merge 9cea46c ew/doc-split-pack-disables-bitmap later to maint).
   (merge fa72245 ew/normal-to-e later to maint).
   (merge 2e39a24 rn/glossary-typofix later to maint).
   (merge cadfbef sb/clean-test-fix later to maint).