首先使用git远程更新，使您的远程参考更新到最新。然后你可以做以下几件事中的一件，比如:

Git status -uno将告诉你你正在跟踪的分支是在前面、后面还是已经偏离。如果没有显示，则本地和远程是相同的。 Git show-branch *master会显示所有以master结尾的分支中的提交(例如master和origin/master)。

如果你在git远程更新(git remote -v update)中使用-v，你可以看到哪些分支被更新了，所以你真的不需要任何进一步的命令。

However, it looks like you want to do this in a script or program and end up with a true/false value. If so, there are ways to check the relationship between your current HEAD commit and the head of the branch you're tracking, although since there are four possible outcomes you can't reduce it to a yes/no answer. However, if you're prepared to do a pull --rebase then you can treat "local is behind" and "local has diverged" as "need to pull", and the other two ("local is ahead" and "same") as "don't need to pull".

你可以使用git rev-parse <ref>获得任何ref的提交id，所以你可以对master和origin/master这样做并比较它们。如果它们相等，那么分支是相同的。如果它们不相等，你想知道哪个在前面。使用git merge-base master origin/master会告诉你两个分支的共同祖先，如果它们没有分叉，这将是一个或另一个相同的。如果您得到三个不同的id，则分支已经分离。

To do this properly, eg in a script, you need to be able to refer to the current branch, and the remote branch it's tracking. The bash prompt-setting function in /etc/bash_completion.d has some useful code for getting branch names. However, you probably don't actually need to get the names. Git has some neat shorthands for referring to branches and commits (as documented in git rev-parse --help). In particular, you can use @ for the current branch (assuming you're not in a detached-head state) and @{u} for its upstream branch (eg origin/master). So git merge-base @ @{u} will return the (hash of the) commit at which the current branch and its upstream diverge and git rev-parse @ and git rev-parse @{u} will give you the hashes of the two tips. This can be summarized in the following script:

#!/bin/sh

UPSTREAM=${1:-'@{u}'}
LOCAL=$(git rev-parse @)
REMOTE=$(git rev-parse "$UPSTREAM")
BASE=$(git merge-base @ "$UPSTREAM")

if [ $LOCAL = $REMOTE ]; then
    echo "Up-to-date"
elif [ $LOCAL = $BASE ]; then
    echo "Need to pull"
elif [ $REMOTE = $BASE ]; then
    echo "Need to push"
else
    echo "Diverged"
fi

注意:旧版本的git不允许@单独使用，所以你可能不得不使用@{0}代替。

UPSTREAM=${1:-'@{u}'}允许你显式地传递一个上游分支，以防你想检查一个不同于当前分支配置的远程分支。这通常是remotename/branchname的形式。如果不指定参数，默认值为@{u}。

该脚本假设您已经首先进行了git获取或git远程更新，以使跟踪分支更新到最新。我没有把这个构建到脚本中，因为它更灵活，能够将抓取和比较作为单独的操作，例如，如果你想比较而不抓取，因为你最近已经获取了。

我会按照布罗尔的建议去做。下面的一行脚本使用您最后提交的版本的SHA1，并将其与远程原始版本的SHA1进行比较，仅在它们不同时才进行更改。 基于git pull或git fetch的解决方案更加轻量级。

[ `git log --pretty=%H ...refs/heads/master^` != `git ls-remote origin
-h refs/heads/master |cut -f1` ] && git pull

下面的脚本运行良好。

changed=0
git remote update && git status -uno | grep -q 'Your branch is behind' && changed=1
if [ $changed = 1 ]; then
    git pull
    echo "Updated successfully";
else
    echo "Up-to-date"
fi

自动化git拉取所需的分支: 例如:./pull.sh "origin/main"

pull.sh

#!/bin/bash

UPSTREAM=${1:-'@{u}'}
DIFFCOMM=$(git fetch origin --quiet; git rev-list HEAD..."$UPSTREAM" --count)
if [ "$DIFFCOMM" -gt 0 ]; then
  echo "Pulling $UPSTREAM";
  git pull;
else
  echo "Up-to-date";
fi

这一行在zsh中为我工作(来自@Stephen Haberman的回答)

git fetch; [ $(git rev-parse HEAD) = $(git rev-parse @{u}) ] \
    && echo "Up to date" || echo "Not up to date"

所有这些复杂的建议，而解决方案却如此简单:

#!/bin/bash

BRANCH="<your branch name>"
LAST_UPDATE=`git show --no-notes --format=format:"%H" $BRANCH | head -n 1`
LAST_COMMIT=`git show --no-notes --format=format:"%H" origin/$BRANCH | head -n 1`

git remote update
if [ $LAST_COMMIT != $LAST_UPDATE ]; then
        echo "Updating your branch $BRANCH"
        git pull --no-edit
else
        echo "No updates available"
fi