update branches

for branches, please refer to git-branches.

for local objects, they are stored in .git/objects/

for references, they are in .git/refs/heads/

for remotes, .git/refs/remotes/

git fetch

link: git-fetch

git fetch <remote> <branch>    ==> fetch one/all of branches from the repository

git fetch --all        ==> more power commands

git fetch --dry-run    ==> perform a demo, but not apply them

typical <refspec> variable is like:

fetch = +refs/heads/*:refs/remotes/origin/*

fetch all branches exist in origin that refs matches the refs/heads/*, and update the corresponding remote-tracking branches in the ref/remotes/origin/*, even no fast-forward is performed because of the + sign is specified (cause it means force update).

special example:

git fetch master: == git fetch origin master, means “fetch the master branch but I do not explicitly say what remote-tracking branch to update, only the master branch will be updated.

git pull

link: git-pull

in default, git pull == git fetch & git merge FETCH_HEAD,

more: git pull --rebase == git fetch & git rebase FETCH_HEAD, it does not create the new local tracking history, instead it continues the remote records and moves the current heads on it.

illustration

   --A---B---C  (remote origin/master)
 /
D---E---F---G  (local master)



@git pull

   --A---B---C    (remote origin/master)
 /             \
D---E---F---G---H    (local master)      [new commit on H]


@git pull --rebase

D---A---B---C---E'---F'---G'  (local master)    [append local commits on C]
            |
       remote origin/master

usage:

git pull [<options>] [<repository> [<refspec>...]]

git merge

link: git-merge

usage:

git merge [<options>] [<branch/tag-1> <branch/tag-2> ...]

git push

link: git-push

usage:

git push <remote> <branch>