分布式版本控制系统，Git v2.0 发布

Git 是一个分布式版本控制系统，可以记录文件变化，以便在需要时退回过去某个时间点的状态，它与SVN最大不同在于，GIT是直接快照，而非比较差异，因此它拥有许多令人兴奋的特性，如简便的分支管理、高效率的分布式控制等等。

Git v2.0 发布日志  ======================    向后兼容性注意事项  ----------------------------    When "git push [$there]" does not say what to push, we have used the  traditional "matching" semantics so far (all your branches were sent  to the remote as long as there already are branches of the same name  over there).  In Git 2.0, the default is now the "simple" semantics,  which pushes:     - only the current branch to the branch with the same name, and only     when the current branch is set to integrate with that remote     branch, if you are pushing to the same remote as you fetch from; or     - only the current branch to the branch with the same name, if you     are pushing to a remote that is not where you usually fetch from.    You can use the configuration variable "push.default" to change  this.  If you are an old-timer who wants to keep using the  "matching" semantics, you can set the variable to "matching", for  example.  Read the documentation for other possibilities.    When "git add -u" and "git add -A" are run inside a subdirectory  without specifying which paths to add on the command line, they  operate on the entire tree for consistency with "git commit -a" and  other commands (these commands used to operate only on the current  subdirectory).  Say "git add -u ." or "git add -A ." if you want to  limit the operation to the current directory.    "git add <path>" is the same as "git add -A <path>" now, so that  "git add dir/" will notice paths you removed from the directory and  record the removal.  In older versions of Git, "git add <path>" used  to ignore removals.  You can say "git add --ignore-removal <path>" to  add only added or modified paths in <path>, if you really want to.    The "-q" option to "git diff-files", which does *NOT* mean "quiet",  has been removed (it told Git to ignore deletion, which you can do  with "git diff-files --diff-filter=d").      Updates since v1.9 series  -------------------------    Foreign interfaces, subsystems and ports.      UI, Workflows & Features     * The "simple" mode is the default for "git push".     * "git add -u" and "git add -A", when run without any pathspec, is a     tree-wide operation even when run inside a subdirectory of a     working tree.     * "git add <path> is the same as "git add -A <path>" now.     * "core.statinfo" configuration variable, which is a     never-advertised synonym to "core.checkstat", has been removed.     * The "-q" option to "git diff-files", which does *NOT* mean     "quiet", has been removed (it told Git to ignore deletion, which     you can do with "git diff-files --diff-filter=d").     * Many commands that creates commits, e.g. "pull", "rebase",     learned to take the --gpg-sign option on the command line.     * "git commit" can be told to always GPG sign the resulting commit     by setting "commit.gpgsign" configuration variable to true (the     command line option --no-gpg-sign should override it).     * "git pull" can be told to only accept fast-forward by setting the     new "pull.ff" configuration.     * "git reset" learned "-N" option, which does not reset the index     fully for paths the index knows about but the tree-ish the command     resets to does not (these paths are kept as intend-to-add entries).     * Newly cloned submodule repositories by "git submodule update",     when the "checkout" update mode is used, will be on a local     branch instead of on a detached HEAD, just like submodules added     with "git submodule add".      Performance, Internal Implementation, etc.     * The bitmap-index feature from JGit has been ported, which should     significantly improve performance when serving objects form a     repository that uses it.     * The way "git log --cc" shows a combined diff against multiple     parents have been optimized.     * The prefixcmp() and suffixcmp() functions are gone.  Use     starts_with() and ends_with(), and also consider if skip_prefix()     suits your needs better when using the former.      Also contains various documentation updates and code clean-ups.      Fixes since v1.9 series  -----------------------    Unless otherwise noted, all the fixes since v1.9 in the maintenance  track are contained in this release (see the maintenance releases'  notes for details).     * "merge-recursive" was broken in 1.7.7 era and stopped working in     an empty (temporary) working tree, when there are renames     involved.  This has been corrected.     (merge 6e2068a bk/refresh-missing-ok-in-merge-recursive later to maint.)     * "git rev-parse" was loose in rejecting command line arguments     that do not make sense, e.g. "--default" without the required     value for that option.     (merge a43219f ds/rev-parse-required-args later to maint.)     * include.path variable (or any variable that expects a path that     can use ~username expansion) in the configuration file is not a     boolean, but the code failed to check it.     (merge 67beb60 jk/config-path-include-fix later to maint.)     * Commands that take pathspecs on the command line misbehaved when     the pathspec is given as an absolute pathname (which is a     practice not particularly encouraged) that points at a symbolic     link in the working tree.     (merge later 655ee9e mw/symlinks to maint.)     * "git diff --quiet -- pathspec1 pathspec2" sometimes did not return     correct status value.     (merge f34b205 nd/diff-quiet-stat-dirty later to maint.)     * Attempting to deepen a shallow repository by fetching over smart     HTTP transport failed in the protocol exchange, when no-done     extension was used.  The fetching side waited for the list of     shallow boundary commits after the sending end stopped talking to     it.     (merge 0232852 nd/http-fetch-shallow-fix later to maint.)     * Allow "git cmd path/", when the 'path' is where a submodule is     bound to the top-level working tree, to match 'path', despite the     extra and unnecessary trailing slash (such a slash is often     given by command line completion).     (merge 2e70c01 nd/submodule-pathspec-ending-with-slash later to maint.)