diff options
| -rw-r--r-- | Documentation/git-checkout.txt | 54 | ||||
| -rw-r--r-- | Documentation/repository-layout.txt | 6 |
2 files changed, 58 insertions, 2 deletions
diff --git a/Documentation/git-checkout.txt b/Documentation/git-checkout.txt index fbdbadc74f..c44a4a8004 100644 --- a/Documentation/git-checkout.txt +++ b/Documentation/git-checkout.txt @@ -9,7 +9,7 @@ SYNOPSIS -------- [verse] 'git-checkout' [-f] [-b <new_branch> [-l]] [-m] [<branch>] -'git-checkout' [-m] [<branch>] <paths>... +'git-checkout' [<branch>] <paths>... DESCRIPTION ----------- @@ -63,7 +63,57 @@ and mark the resolved paths with `git update-index`. <branch>:: Branch to checkout; may be any object ID that resolves to a - commit. Defaults to HEAD. + commit. Defaults to HEAD. ++ +When this parameter names a non-branch (but still a valid commit object), +your HEAD becomes 'detached'. + + +Detached HEAD +------------- + +It is sometimes useful to be able to 'checkout' a commit that is +not at the tip of one of your branches. The most obvious +example is to check out the commit at a tagged official release +point, like this: + +------------ +$ git checkout v2.6.18 +------------ + +Earlier versions of git did not allow this and asked you to +create a temporary branch using `-b` option, but starting from +version 1.5.0, the above command 'detaches' your HEAD from the +current branch and directly point at the commit named by the tag +(`v2.6.18` in the above example). + +You can use usual git commands while in this state. You can use +`git-reset --hard $othercommit` to further move around, for +example. You can make changes and create a new commit on top of +a detached HEAD. You can even create a merge by using `git +merge $othercommit`. + +The state you are in while your HEAD is detached is not recorded +by any branch (which is natural --- you are not on any branch). +What this means is that you can discard your temporary commits +and merges by switching back to an existing branch (e.g. `git +checkout master`), and a later `git prune` or `git gc` would +garbage-collect them. + +The command would refuse to switch back to make sure that you do +not discard your temporary state by mistake when your detached +HEAD is not pointed at by any existing ref. If you did want to +save your state (e.g. "I was interested in the fifth commit from +the top of 'master' branch", or "I made two commits to fix minor +bugs while on a detached HEAD" -- and if you do not want to lose +these facts), you can create a new branch and switch to it with +`git checkout -b newbranch` so that you can keep building on +that state, or tag it first so that you can come back to it +later and switch to the branch you wanted to switch to with `git +tag that_state; git checkout master`. On the other hand, if you +did want to discard the temporary state, you can give `-f` +option (e.g. `git checkout -f master`) to override this +behaviour. EXAMPLES diff --git a/Documentation/repository-layout.txt b/Documentation/repository-layout.txt index 0fdd36614d..7c8c141419 100644 --- a/Documentation/repository-layout.txt +++ b/Documentation/repository-layout.txt @@ -91,6 +91,12 @@ HEAD:: 'name' does not (yet) exist. In some legacy setups, it is a symbolic link instead of a symref that points at the current branch. ++ +HEAD can also record a specific commit directly, instead of +being a symref to point at the current branch. Such a state +is often called 'detached HEAD', and almost all commands work +identically as normal. See gitlink:git-checkout[1] for +details. branches:: A slightly deprecated way to store shorthands to be used |