git pull 的参数如果 git 不设置 pull 参数，可能出现的状况是什么？
答：如果使用的是 git version 2.27.0，则会提示用户对 pull 的默认操作进行设置，一共有三个选项。示例如下
$ git pull origin master
warning: 不建议在没有为偏离分支指定合并策略时执行 pull 操作。 您可以在执行下一次
pull 操作之前执行下面一条命令来抑制本消息：
git config pull.rebase false # 合并（缺省策略）
git config pull.rebase true # 变基
git config pull.ff only # 仅快进
您可以将 "git config" 替换为 "git config --global" 以便为所有仓库设置
缺省的配置项。您也可以在每次执行 pull 命令时添加 --rebase、--no-rebase，
或者 --ff-only 参数覆盖缺省设置。
来自 github.com:iridiumcao/blog
* branch master -> FETCH_HEAD
已经是最新的。
pull.rebase 执行 git pull 时使用是否变基（rebase）
false：如果远程分支有新的 commit, 则本地创建一个新的合并提交，将远程分支的变化合并到本地分支上。true：如果远程分支有新的 commit, 则将本地的提交放到远程分支的最新提交之后，使得提交历史更加线性，不会产生额外的合并提交。pull.ff
false: create an extra merge commit in such a case (equivalent to giving the --no-ff option from the command line)only：这个命令告诉Git在执行git pull命令时只允许快进（fast-forward）合并，等价于 --ff-only.如果远程分支能够直接合并到本地分支而不产生新的提交，就会执行快进合并；否则，会出现合并冲突的情况。-ff，没有分叉，就 fast-forward, 有分叉，就生成合并 commit下面是来自官方文档的内容
pull.rebase
When true, rebase branches on top of the fetched branch, instead of merging the default branch from the default remote when “git pull” is run. See “branch.
.rebase" for setting this on a per-branch basis. When
merges(or justm), pass the--rebase-mergesoption to git rebase so that the local merge commits are included in the rebase (see git-rebase for details).When the value is
interactive(or justi), the rebase is run in interactive mode.NOTE: this is a possibly dangerous operation; do not use it unless you understand the implications (see git-rebase for details).
pull.ff
By default, Git does not create an extra merge commit when merging a commit that is a descendant of the current commit. Instead, the tip of the current branch is fast-forwarded. When set to
false, this variable tells Git to create an extra merge commit in such a case (equivalent to giving the--no-ffoption from the command line). When set toonly, only such fast-forward merges are allowed (equivalent to giving the--ff-onlyoption from the command line). This setting overridesmerge.ffwhen pulling.