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.
   (merge f916ab0 ew/send-email-readable-message-id later to maint).

 * "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).


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.
   (merge 65a3629 mp/upload-pack-use-embedded-args later to maint).

 * 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.
   (merge 11e6b3f jk/startup-info later to maint).

 * 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.
   (merge 8fbb03a sb/clone-t57-t56 later to maint).

 * The tests that involve running httpd leaked the system-wide
   configuration in /etc/gitconfig to the tested environment.
   (merge 1fad503 jk/test-httpd-config-nosystem later to maint).

 * Build updates for MSVC.
   (merge 0ef60af ss/msvc later to maint).

 * 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.
   (merge 274db84 jk/check-repository-format later to maint).

 * 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).


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.
   (merge 24990b2 jk/config-get-urlmatch later to maint).

 * 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.
   (merge fc7d47f jk/rev-parse-local-env-vars later to maint).

 * "git index-pack --keep[=<msg>] pack-$name.pack" simply did not work.
   (merge 0e94242 jc/maint-index-pack-keep later to maint).

 * Fetching of history by naming a commit object name directly didn't
   work across remote-curl transport.
   (merge 754ecb1 gf/fetch-pack-direct-object-fetch later to maint).

 * A small memory leak in an error codepath has been plugged in xdiff
   code.
   (merge 87f1625 rj/xdiff-prepare-plug-leak-on-error-codepath later to maint).

 * strbuf_getwholeline() did not NUL-terminate the buffer on certain
   corner cases in its error codepath.
   (merge b709043 jk/getwholeline-getdelim-empty later to maint).

 * "git mergetool" did not work well with conflicts that both sides
   deleted.
   (merge a298604 da/mergetool-delete-delete-conflict later to maint).

 * "git send-email" had trouble parsing alias file in mailrc format
   when lines in it had trailing whitespaces on them.
   (merge a277d1e jk/send-email-rtrim-mailrc-alias later to maint).

 * 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.
   (merge b64c1e0 ss/commit-squash-msg later to maint).

 * "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).
   (merge b84e65d jv/merge-nothing-into-void later to maint).

 * 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.
   (merge f292244 ky/branch-d-worktree later to maint).

 * 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.
   (merge 18eb3a9 ky/branch-m-worktree later to maint).

 * "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.
   (merge ca4e3ca sg/diff-multiple-identical-renames later to maint).

 * "git send-pack --all <there>" was broken when its command line
   option parsing was written in the 2.6 timeframe.
   (merge c677756 sk/send-pack-all-fix later to maint).

 * "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.
   (merge b73a1bc es/format-patch-doc-hide-no-patch later to maint).

 * 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.
   (merge a08feb8 tb/blame-force-read-cache-to-workaround-safe-crlf later to maint).

 * 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).
   (merge 95c38fb jk/branch-shortening-funny-symrefs later to maint).

 * 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.
   (merge 1f15ba1 sb/submodule-helper-clone-regression-fix later to maint).

 * "git commit" misbehaved in a few minor ways when an empty message
   is given via -m '', all of which has been corrected.
   (merge 27014cb ad/commit-have-m-option later to maint).

 * Support for CRAM-MD5 authentication method in "git imap-send" did
   not work well.
   (merge eb94ee7 ky/imap-send later to maint).

 * 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.
   (merge 87f8a0b jc/http-socks5h later to maint).

 * "git config" had a codepath that tried to pass a NULL to
   printf("%s"), which nobody seems to have noticed.
   (merge 1cae428 jk/do-not-printf-NULL later to maint).

 * 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 e53a64b ad/cygwin-wants-rename later to maint).

 * "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 c4b2751 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).

 * Other minor clean-ups and documentation updates
   (merge aed7480 mm/lockfile-error-message later to maint).
   (merge bfee614 jc/index-pack later to maint).
   (merge f870899 ss/exc-flag-is-a-collection-of-bits later to maint).
   (merge dde7891 pb/t7502-drop-dup later to maint).
   (merge 3bd1b51 cc/doc-recommend-performance-trace-to-file later to maint).
   (merge 7d5e9c9 jk/credential-cache-comment-exit later to maint).
   (merge 16a86d4 nd/apply-doc later to maint).
   (merge c3f6b85 pb/opt-cmdmode-doc later to maint).
   (merge 30211fb oa/doc-diff-check later to maint).
   (merge 01d98e8 ak/use-hashmap-iter-first-in-submodule-config later to maint).
   (merge 8b5a3e9 kn/for-each-tag-branch later to maint).
   (merge 9c60d9f sb/misc-cleanups later to maint).
   (merge 7a6a44c cc/apply later to maint).
   (merge 8e9b208 js/mingw-tests-2.8 later to maint).
   (merge d55de70 jc/makefile-redirection-stderr later to maint).
   (merge 4232b21 ep/trace-doc-sample-fix later to maint).
   (merge ef8c95e ew/send-email-drop-data-dumper later to maint).
   (merge 24041d6 jc/xstrfmt-null-with-prec-0 later to maint).
   (merge 7bec7f5 jk/use-write-script-more later to maint).