At any point you can view the history of your changes using
------------------------------------------------
-$ git whatchanged
+$ git log
------------------------------------------------
If you also want to see complete diffs at each step, use
------------------------------------------------
-$ git whatchanged -p
+$ git log -p
------------------------------------------------
Managing branches
"master". Alice could request a different branch by adding the name
of the branch to the end of the git pull command line.
-This merges Bob's changes into her repository; "git whatchanged" will
+This merges Bob's changes into her repository; "git log" will
now show the new commits. If Alice has made her own changes in the
meantime, then Bob's changes will be merged in, and she will need to
manually fix any conflicts.
of Bob's line of development without doing any merging). Then
-------------------------------------
-$ git whatchanged -p master..bob-incoming
+$ git log -p master..bob-incoming
-------------------------------------
shows a list of all the changes that Bob made since he branched from
that various users push changes to; see gitlink:git-push[1] and
link:cvs-migration.html[git for CVS users].
-Keeping track of history
-------------------------
+Exploring history
+-----------------
-Git history is represented as a series of interrelated commits. The
-most recent commit in the currently checked-out branch can always be
-referred to as HEAD, and the "parent" of any commit can always be
-referred to by appending a caret, "^", to the end of the name of the
-commit. So, for example,
+Git history is represented as a series of interrelated commits. We
+have already seen that the git log command can list those commits.
+Note that first line of each git log entry also gives a name for the
+commit:
-------------------------------------
-git diff HEAD^ HEAD
+$ git log
+commit c82a22c39cbc32576f64f5c6b3f24b99ea8149c7
+Author: Junio C Hamano <junkio@cox.net>
+Date: Tue May 16 17:18:22 2006 -0700
+
+ merge-base: Clarify the comments on post processing.
-------------------------------------
-shows the difference between the most-recently checked-in state of
-the tree and the previous state, and
+We can give this name to git show to see the details about this
+commit.
-------------------------------------
-git diff HEAD^^ HEAD^
+$ git show c82a22c39cbc32576f64f5c6b3f24b99ea8149c7
-------------------------------------
-shows the difference between that previous state and the state two
-commits ago. Also, HEAD~5 can be used as a shorthand for HEAD{caret}{caret}{caret}{caret}{caret},
-and more generally HEAD~n can refer to the nth previous commit.
-Commits representing merges have more than one parent, and you can
-specify which parent to follow in that case; see
-gitlink:git-rev-parse[1].
+But there other ways to refer to commits. You can use any initial
+part of the name that is long enough to uniquely identify the commit:
+
+-------------------------------------
+$ git show c82a22c39c # the first few characters of the name are
+ # usually enough
+$ git show HEAD # the tip of the current branch
+$ git show experimental # the tip of the "experimental" branch
+-------------------------------------
-The name of a branch can also be used to refer to the most recent
-commit on that branch; so you can also say things like
+Every commit has at least one "parent" commit, which points to the
+previous state of the project:
-------------------------------------
-git diff HEAD experimental
+$ git show HEAD^ # to see the parent of HEAD
+$ git show HEAD^^ # to see the grandparent of HEAD
+$ git show HEAD~4 # to see the great-great grandparent of HEAD
-------------------------------------
-to see the difference between the most-recently committed tree in
-the current branch and the most-recently committed tree in the
-experimental branch.
+Note that merge commits may have more than one parent:
-But you may find it more useful to see the list of commits made in
-the experimental branch but not in the current branch, and
+-------------------------------------
+$ git show HEAD^1 # show the first parent of HEAD (same as HEAD^)
+$ git show HEAD^2 # show the second parent of HEAD
+-------------------------------------
+
+You can also give commits names of your own; after running
-------------------------------------
-git whatchanged HEAD..experimental
+$ git-tag v2.5 1b2e1d63ff
-------------------------------------
-will do that, just as
+you can refer to 1b2e1d63ff by the name "v2.5". If you intend to
+share this name with other people (for example, to identify a release
+version), you should create a "tag" object, and perhaps sign it; see
+gitlink:git-tag[1] for details.
+
+Any git command that needs to know a commit can take any of these
+names. For example:
-------------------------------------
-git whatchanged experimental..HEAD
+$ git diff v2.5 HEAD # compare the current HEAD to v2.5
+$ git branch stable v2.5 # start a new branch named "stable" based
+ # at v2.5
+$ git reset --hard HEAD^ # reset your current branch and working
+ # directory its state at HEAD^
-------------------------------------
-will show the list of commits made on the HEAD but not included in
-experimental.
+Be careful with that last command: in addition to losing any changes
+in the working directory, it will also remove all later commits from
+this branch. If this branch is the only branch containing those
+commits, they will be lost. (Also, don't use "git reset" on a
+publicly-visible branch that other developers pull from, as git will
+be confused by history that disappears in this way.)
-You can also give commits convenient names of your own: after running
+The git grep command can search for strings in any version of your
+project, so
-------------------------------------
-$ git-tag v2.5 HEAD^^
+$ git grep "hello" v2.5
-------------------------------------
-you can refer to HEAD^^ by the name "v2.5". If you intend to share
-this name with other people (for example, to identify a release
-version), you should create a "tag" object, and perhaps sign it; see
-gitlink:git-tag[1] for details.
+searches for all occurences of "hello" in v2.5.
-You can revisit the old state of a tree, and make further
-modifications if you wish, using git branch: the command
+If you leave out the commit name, git grep will search any of the
+files it manages in your current directory. So
-------------------------------------
-$ git branch stable-release v2.5
+$ git grep "hello"
-------------------------------------
-will create a new branch named "stable-release" starting from the
-commit which you tagged with the name v2.5.
+is a quick way to search just the files that are tracked by git.
-You can reset the state of any branch to an earlier commit at any
-time with
+Many git commands also take sets of commits, which can be specified
+in a number of ways. Here are some examples with git log:
-------------------------------------
-$ git reset --hard v2.5
+$ git log v2.5..v2.6 # commits between v2.5 and v2.6
+$ git log v2.5.. # commits since v2.5
+$ git log --since="2 weeks ago" # commits from the last 2 weeks
+$ git log v2.5.. Makefile # commits since v2.5 which modify
+ # Makefile
-------------------------------------
-This will remove all later commits from this branch and reset the
-working tree to the state it had when the given commit was made. If
-this branch is the only branch containing the later commits, those
-later changes will be lost. Don't use "git reset" on a
-publicly-visible branch that other developers pull from, as git will
-be confused by history that disappears in this way.
+You can also give git log a "range" of commits where the first is not
+necessarily an ancestor of the second; for example, if the tips of
+the branches "stable-release" and "master" diverged from a common
+commit some time ago, then
+
+-------------------------------------
+$ git log stable..experimental
+-------------------------------------
+
+will list commits made in the experimental branch but not in the
+stable branch, while
+
+-------------------------------------
+$ git log experimental..stable
+-------------------------------------
+
+will show the list of commits made on the stable branch but not
+the experimental branch.
+
+The "git log" command has a weakness: it must present commits in a
+list. When the history has lines of development that diverged and
+then merged back together, the order in which "git log" presents
+those commits is meaningless.
+
+Most projects with multiple contributors (such as the linux kernel,
+or git itself) have frequent merges, and gitk does a better job of
+visualizing their history. For example,
+
+-------------------------------------
+$ gitk --since="2 weeks ago" drivers/
+-------------------------------------
+
+allows you to browse any commits from the last 2 weeks of commits
+that modified files under the "drivers" directory. (Note: you can
+adjust gitk's fonts by holding down the control key while pressing
+"-" or "+".)
+
+Finally, most commands that take filenames will optionally allow you
+to precede any filename by a commit, to specify a particular version
+of the file:
+
+-------------------------------------
+$ git diff v2.5:Makefile HEAD:Makefile.in
+-------------------------------------
+
+You can also use "git cat-file -p" to see any such file:
+
+-------------------------------------
+$ git cat-file -p v2.5:Makefile
+-------------------------------------
Next Steps
----------
-Some good commands to explore next:
+This tutorial should be enough to perform basic distributed revision
+control for your projects. However, to fully understand the depth
+and power of git you need to understand two simple ideas on which it
+is based:
+
+ * The object database is the rather elegant system used to
+ store the history of your project--files, directories, and
+ commits.
+
+ * The index file is a cache of the state of a directory tree,
+ used to create commits, check out working directories, and
+ hold the various trees involved in a merge.
- * gitlink:git-diff[1]: This flexible command does much more than
- we've seen in the few examples above.
+link:tutorial-2.html[Part two of this tutorial] explains the object
+database, the index file, and a few other odds and ends that you'll
+need to make the most of git.
+
+If you don't want to consider with that right away, a few other
+digressions that may be interesting at this point are:
* gitlink:git-format-patch[1], gitlink:git-am[1]: These convert
series of git commits into emailed patches, and vice versa,
smart enough to perform a close-to-optimal search even in the
case of complex non-linear history with lots of merged branches.
-Other good starting points include link:everyday.html[Everday GIT
-with 20 Commands Or So] and link:cvs-migration.html[git for CVS
-users]. Also, link:core-tutorial.html[A short git tutorial] gives an
-introduction to lower-level git commands for advanced users and
-developers.
+ * link:everyday.html[Everday GIT with 20 Commands Or So]
+
+ * link:cvs-migration.html[git for CVS users].