mirror of
https://github.com/git/git
synced 2024-08-27 11:39:22 +00:00
Documentation: merge: add a section about fast-forward
Novices sometimes find the behavior of 'git merge' in the fast-forward case surprising. Describe it thoroughly. Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Thomas Rast <trast@student.ethz.ch>
This commit is contained in:
parent
30f2bade84
commit
29280311f0
|
@ -86,25 +86,30 @@ would result from the merge already.)
|
|||
If all named commits are already ancestors of `HEAD`, 'git merge'
|
||||
will exit early with the message "Already up-to-date."
|
||||
|
||||
FAST-FORWARD MERGE
|
||||
------------------
|
||||
|
||||
Often the current branch head is an ancestor of the named commit.
|
||||
This is the most common case especially when invoked from 'git
|
||||
pull': you are tracking an upstream repository, you have committed
|
||||
no local changes, and now you want to update to a newer upstream
|
||||
revision. In this case, a new commit is not needed to store the
|
||||
combined history; instead, the `HEAD` (along with the index) is
|
||||
updated to point at the named commit, without creating an extra
|
||||
merge commit.
|
||||
|
||||
This behavior can be suppressed with the `--no-ff` option.
|
||||
|
||||
HOW MERGE WORKS
|
||||
---------------
|
||||
|
||||
A merge is always between the current `HEAD` and one or more
|
||||
commits (usually a branch head or tag).
|
||||
|
||||
Two kinds of merge can happen:
|
||||
|
||||
* `HEAD` is already contained in the merged commit. This is the
|
||||
most common case especially when invoked from 'git pull':
|
||||
you are tracking an upstream repository, have committed no local
|
||||
changes and now you want to update to a newer upstream revision.
|
||||
Your `HEAD` (and the index) is updated to point at the merged
|
||||
commit, without creating an extra merge commit. This is
|
||||
called "Fast-forward".
|
||||
|
||||
* Both the merged commit and `HEAD` are independent and must be
|
||||
tied together by a merge commit that has both of them as its parents.
|
||||
The rest of this section describes this "True merge" case.
|
||||
Except in a fast-forward merge (see above), the branches to be
|
||||
merged must be tied together by a merge commit that has both of them
|
||||
as its parents.
|
||||
The rest of this section describes this "True merge" case.
|
||||
|
||||
The chosen merge strategy merges the two commits into a single
|
||||
new source tree.
|
||||
|
|
Loading…
Reference in a new issue