Clarify two backward incompatible repository options.

[alt-git.git] / Documentation / RelNotes-1.5.0.txt

GIT v1.5.0 Release Notes
========================

Old news
--------

This section is for people who are upgrading from ancient
versions of git.  Although all of the changes in this section
happened before the current v1.4.4 release, they are summarized
here in the v1.5.0 release notes for people who skipped earlier
versions.

As of git v1.5.0 there are some optional features that changes
the repository to allow data to be stored and transferred more
efficiently.  These features are not enabled by default, as they
will make the repository unusable with older versions of git.
Specifically, the available options are:

 - There is a configuration variable core.legacyheaders that
   changes the format of loose objects so that they are more
   efficient to pack and to send out of the repository over git
   native protocol, since v1.4.2.  However, loose objects
   written in the new format cannot be read by git older than
   that version; people fetching from your repository using
   older clients over dumb transports (e.g. http) using older
   versions of git will also be affected.

   To let git use the new loose object format, you have to
   set core.legacyheaders to false.

 - Since v1.4.3, configuration repack.usedeltabaseoffset allows
   packfile to be created in more space efficient format, which
   cannot be read by git older than that version.

   To let git use the new format for packfiles, you have to
   set repack.usedeltabaseoffset to true.

The above two new features are not enabled by default and you
have explicitly to ask for them, because they make repositories
unreadable by older versions of git, and in v1.5.0 we still do
not enable them by default for the same reason.  We will change
this default probably 1 year after 1.4.2's release, when it is
reasonable to expect everybody to have new enough version of
git.

 - 'git pack-refs' appeared in v1.4.4; this command allows tags
   to be accessed much more efficiently than the traditional
   'one-file-per-tag' format.  Older git-native clients can
   still fetch from a repository that packed and pruned refs
   (the server side needs to run the up-to-date version of git),
   but older dumb transports cannot.  Packing of refs is done by
   an explicit user action, either by use of "git pack-refs
   --prune" command or by use of "git gc" command.

 - 'git -p' to paginate anything -- many commands do pagination
   by default on a tty.  Introduced between v1.4.1 and v1.4.2;
   this may surprise old timers.

 - 'git archive' superseded 'git tar-tree' in v1.4.3;

 - 'git cvsserver' was new invention in v1.3.0;

 - 'git repo-config', 'git grep', 'git rebase' and 'gitk' were
   seriously enhanced during v1.4.0 timeperiod.

 - 'gitweb' became part of git.git during v1.4.0 timeperiod and
   seriously modified since then.

 - reflog is an v1.4.0 invention.  This allows you to name a
   revision that a branch used to be at (e.g. "git diff
   master@{yesterday} master" allows you to see changes since
   yesterday's tip of the branch).


Updates in v1.5.0 since v1.4.4 series
-------------------------------------

* Index manipulation

 - git-add is to add contents to the index (aka "staging area"
   for the next commit), whether the file the contents happen to
   be is an existing one or a newly created one.

 - git-add without any argument does not add everything
   anymore.  Use 'git-add .' instead.  Also you can add
   otherwise ignored files with an -f option.

 - git-add tries to be more friendly to users by offering an
   interactive mode ("git-add -i").

 - git-commit <path> used to refuse to commit if <path> was
   different between HEAD and the index (i.e. update-index was
   used on it earlier).  This check was removed.

 - git-rm is much saner and safer.  It is used to remove paths
   from both the index file and the working tree, and makes sure
   you are not losing any local modification before doing so.

 - git-reset <tree> <paths>... can be used to revert index
   entries for selected paths.

 - git-update-index is much less visible.  Many suggestions to
   use the command in git output and documentation have now been
   replaced by simpler commands such as "git add" or "git rm".


* Repository layout and objects transfer

 - The data for origin repository is stored in the configuration
   file $GIT_DIR/config, not in $GIT_DIR/remotes/, for newly
   created clones.  The latter is still supported and there is
   no need to convert your existing repository if you are
   already comfortable with your workflow with the layout.

 - git-clone always uses what is known as "separate remote"
   layout for a newly created repository with a working tree.

   A repository with the separate remote layout starts with only
   one default branch, 'master', to be used for your own
   development.  Unlike the traditional layout that copied all
   the upstream branches into your branch namespace (while
   renaming their 'master' to your 'origin'), the new layout
   puts upstream branches into local "remote-tracking branches"
   with their own namespace. These can be referenced with names
   such as "origin/$upstream_branch_name" and are stored in
   .git/refs/remotes rather than .git/refs/heads where normal
   branches are stored.

   This layout keeps your own branch namespace less cluttered,
   avoids name collision with your upstream, makes it possible
   to automatically track new branches created at the remote
   after you clone from it, and makes it easier to interact with
   more than one remote repository (you can use "git remote" to
   add other repositories to track).  There might be some
   surprises:

   * 'git branch' does not show the remote tracking branches.
     It only lists your own branches.  Use '-r' option to view
     the tracking branches.

   * If you are forking off of a branch obtained from the
     upstream, you would have done something like 'git branch
     my-next next', because traditional layout dropped the
     tracking branch 'next' into your own branch namespace.
     With the separate remote layout, you say 'git branch next
     origin/next', which allows you to use the matching name
     'next' for your own branch.  It also allows you to track a
     remote other than 'origin' (i.e. where you initially cloned
     from) and fork off of a branch from there the same way
     (e.g. "git branch mingw j6t/master").

   Repositories initialized with the traditional layout continue
   to work.

 - New branches that appear on the origin side after a clone is
   made are also tracked automatically.  This is done with an
   wildcard refspec "refs/heads/*:refs/remotes/origin/*", which
   older git does not understand, so if you clone with 1.5.0,
   you would need to downgrade remote.*.fetch in the
   configuration file to specify each branch you are interested
   in individually if you plan to fetch into the repository with
   older versions of git (but why would you?).

 - Similarly, wildcard refspec "refs/heads/*:refs/remotes/me/*"
   can be given to "git-push" command to update the tracking
   branches that is used to track the repository you are pushing
   from on the remote side.

 - git-branch and git-show-branch know remote tracking branches
   (use the command line switch "-r" to list only tracked branches).

 - git-push can now be used to delete a remote branch or a tag.
   This requires the updated git on the remote side (use "git
   push <remote> :refs/heads/<branch>" to delete "branch").

 - git-push more aggressively keeps the transferred objects
   packed.  Earlier we recommended to monitor amount of loose
   objects and repack regularly, but you should repack when you
   accumulated too many small packs this way as well.  Updated
   git-count-objects helps you with this.

 - git-fetch also more aggressively keeps the transferred objects
   packed.  This behavior of git-push and git-fetch can be
   tweaked with a single configuration transfer.unpacklimit (but
   usually there should not be any need for a user to tweak it).

 - A new command, git-remote, can help you manage your remote
   tracking branch definitions.

 - You may need to specify explicit paths for upload-pack and/or
   receive-pack due to your ssh daemon configuration on the
   other end.  This can now be done via remote.*.uploadpack and
   remote.*.receivepack configuration.


* Bare repositories

 - Certain commands change their behavior in a bare repository
   (i.e. a repository without associated working tree).  We use
   a fairly conservative heuristic (if $GIT_DIR is ".git", or
   ends with "/.git", the repository is not bare) to decide if a
   repository is bare, but "core.bare" configuration variable
   can be used to override the heuristic when it misidentifies
   your repository.

 - git-fetch used to complain updating the current branch but
   this is now allowed for a bare repository.  So is the use of
   'git-branch -f' to update the current branch.

 - Porcelain-ish commands that require a working tree refuses to
   work in a bare repository.


* Reflog

 - Reflog records the history from the view point of the local
   repository. In other words, regardless of the real history,
   the reflog shows the history as seen by one particular
   repository (this enables you to ask "what was the current
   revision in _this_ repository, yesterday at 1pm?").  This
   facility is enabled by default for repositories with working
   trees, and can be accessed with the "branch@{time}" and
   "branch@{Nth}" notation.

 - "git show-branch" learned showing the reflog data with the
   new -g option.  "git log" has -s option to view reflog
   entries in a more verbose manner.

 - git-branch knows how to rename branches and moves existing
   reflog data from the old branch to the new one.

 - In addition to the reflog support in v1.4.4 series, HEAD
   reference maintains its own log.  "HEAD@{5.minutes.ago}"
   means the commit you were at 5 minutes ago, which takes
   branch switching into account.  If you want to know where the
   tip of your current branch was at 5 minutes ago, you need to
   explicitly say its name (e.g. "master@{5.minutes.ago}") or
   omit the refname altogether i.e. "@{5.minutes.ago}".

 - The commits referred to by reflog entries are now protected
   against pruning.  The new command "git reflog expire" can be
   used to truncate older reflog entries and entries that refer
   to commits that have been pruned away previously with older
   versions of git.

   Existing repositories that have been using reflog may get
   complaints from fsck-objects and may not be able to run
   git-repack, if you had run git-prune from older git; please
   run "git reflog expire --stale-fix --all" first to remove
   reflog entries that refer to commits that are no longer in
   the repository when that happens.


* Crufts removal

 - We used to say "old commits are retrievable using reflog and
   'master@{yesterday}' syntax as long as you haven't run
   git-prune".  We no longer have to say the latter half of the
   above sentence, as git-prune does not remove things reachable
   from reflog entries.

 - 'git-prune' by default does not remove _everything_
   unreachable, as there is a one-day grace period built-in.

 - There is a toplevel garbage collector script, 'git-gc', that
   runs periodic cleanup functions, including 'git-repack -a -d',
   'git-reflog expire', 'git-pack-refs --prune', and 'git-rerere
   gc'.

 - The output from fsck ("fsck-objects" is called just "fsck"
   now, but the old name continues to work) was needlessly
   alarming in that it warned missing objects that are reachable
   only from dangling objects.  This has been corrected and the
   output is much more useful.


* Detached HEAD

 - You can use 'git-checkout' to check out an arbitrary revision
   or a tag as well, instead of named branches.  This will
   dissociate your HEAD from the branch you are currently on.

   A typical use of this feature is to "look around".  E.g.

        $ git checkout v2.6.16
        ... compile, test, etc.
        $ git checkout v2.6.17
        ... compile, test, etc.

 - After detaching your HEAD, you can go back to an existing
   branch with usual "git checkout $branch".  Also you can
   start a new branch using "git checkout -b $newbranch" to
   start a new branch at that commit.

 - You can even pull from other repositories, make merges and
   commits while your HEAD is detached.  Also you can use "git
   reset" to jump to arbitrary commit, while still keeping your
   HEAD detached.

   Remember that a detached state is volatile, i.e. it will be forgotten
   as soon as you move away from it with the checkout or reset command,
   unless a branch is created from it as mentioned above.  It is also
   possible to rescue a lost detached state from the HEAD reflog.


* Packed refs

 - Repositories with hundreds of tags have been paying large
   overhead, both in storage and in runtime, due to the
   traditional one-ref-per-file format.  A new command,
   git-pack-refs, can be used to "pack" them in more efficient
   representation (you can let git-gc do this for you).

 - Clones and fetches over dumb transports are now aware of
   packed refs and can download from repositories that use
   them.


* Configuration

 - configuration related to color setting are consolidated under
   color.* namespace (older diff.color.*, status.color.* are
   still supported).

 - 'git-repo-config' command is accessible as 'git-config' now.


* Updated features

 - git-describe uses better criteria to pick a base ref.  It
   used to pick the one with the newest timestamp, but now it
   picks the one that is topologically the closest (that is,
   among ancestors of commit C, the ref T that has the shortest
   output from "git-rev-list T..C" is chosen).

 - git-describe gives the number of commits since the base ref
   between the refname and the hash suffix.  E.g. the commit one
   before v2.6.20-rc6 in the kernel repository is:

        v2.6.20-rc5-306-ga21b069

   which tells you that its object name begins with a21b069,
   v2.6.20-rc5 is an ancestor of it (meaning, the commit
   contains everything -rc5 has), and there are 306 commits
   since v2.6.20-rc5.

 - git-describe with --abbrev=0 can be used to show only the
   name of the base ref.

 - git-blame learned a new option, --incremental, that tells it
   to output the blames as they are assigned.  A sample script
   to use it is also included as contrib/blameview.

 - git-blame starts annotating from the working tree by default.


* Less external dependency

 - We no longer require the "merge" program from the RCS suite.
   All 3-way file-level merges are now done internally.

 - The original implementation of git-merge-recursive which was
   in Python has been removed; we have a C implementation of it
   now.

 - git-shortlog is no longer a Perl script.  It no longer
   requires output piped from git-log; it can accept revision
   parameters directly on the command line.


* I18n

 - We have always encouraged the commit message to be encoded in
   UTF-8, but the users are allowed to use legacy encoding as
   appropriate for their projects.  This will continue to be the
   case.  However, a non UTF-8 commit encoding _must_ be
   explicitly set with i18n.commitencoding in the repository
   where a commit is made; otherwise git-commit-tree will
   complain if the log message does not look like a valid UTF-8
   string.

 - The value of i18n.commitencoding in the originating
   repository is recorded in the commit object on the "encoding"
   header, if it is not UTF-8.  git-log and friends notice this,
   and reencodes the message to the log output encoding when
   displaying, if they are different.  The log output encoding
   is determined by "git log --encoding=<encoding>",
   i18n.logoutputencoding configuration, or i18n.commitencoding
   configuration, in the decreasing order of preference, and
   defaults to UTF-8.

 - Tools for e-mailed patch application now default to -u
   behavior; i.e. it always re-codes from the e-mailed encoding
   to the encoding specified with i18n.commitencoding.  This
   unfortunately forces projects that have happily been using a
   legacy encoding without setting i18n.commitencoding to set
   the configuration, but taken with other improvement, please
   excuse us for this very minor one-time inconvenience.


* e-mailed patches

 - See the above I18n section.

 - git-format-patch now enables --binary without being asked.
   git-am does _not_ default to it, as sending binary patch via
   e-mail is unusual and is harder to review than textual
   patches and it is prudent to require the person who is
   applying the patch to explicitly ask for it.

 - The default suffix for git-format-patch output is now ".patch",
   not ".txt".  This can be changed with --suffix=.txt option,
   or setting the config variable "format.suffix" to ".txt".


* Foreign SCM interfaces

 - git-svn now requires the Perl SVN:: libraries, the
   command-line backend was too slow and limited.

 - the 'commit' subcommand of git-svn has been renamed to
   'set-tree', and 'dcommit' is the recommended replacement for
   day-to-day work.

 - git fast-import backend.


* User support

 - Quite a lot of documentation updates.

 - Bash completion scripts have been updated heavily.

 - Better error messages for often used Porcelainish commands.

 - Git GUI.  This is a simple Tk based graphical interface for
   common Git operations.


* Sliding mmap

 - We used to assume that we can mmap the whole packfile while
   in use, but with a large project this consumes huge virtual
   memory space and truly huge ones would not fit in the
   userland address space on 32-bit platforms.  We now mmap huge
   packfile in pieces to avoid this problem.


* Shallow clones

 - There is a partial support for 'shallow' repositories that
   keeps only recent history.  A 'shallow clone' is created by
   specifying how deep that truncated history should be
   (e.g. "git clone --depth=5 git://some.where/repo.git").

   Currently a shallow repository has number of limitations:

   - Cloning and fetching _from_ a shallow clone are not
     supported (nor tested -- so they might work by accident but
     they are not expected to).

   - Pushing from nor into a shallow clone are not expected to
     work.

   - Merging inside a shallow repository would work as long as a
     merge base is found in the recent history, but otherwise it
     will be like merging unrelated histories and may result in
     huge conflicts.

   but this would be more than adequate for people who want to
   look at near the tip of a big project with a deep history and
   send patches in e-mail format.