我该如何避免使用'eval'和'git-for-each-ref'？ [英] How can I avoid using 'eval' in conjunction with 'git-for-each-ref'?

问题描述

git for-each-ref 的大多数高级用法都涉及 eval 。例如， git- for-each-ref 手册页使用 eval 来执行 fmt code> variable：

 ＃！/ bin / sh 
 
 fmt ='
r =％（refname）
＃...省略，简洁... 
'
 
 eval =`git for-each- ref --shell --format =$ fmt\ 
＃...省略，简明... 
 refs / tags` 
 eval$ eval
  

然而， eval 与安全风险相关联;尽可能避免它，被认为是良好的做法。

这是一个真实的例子，改编自这个答案：

 ＃！/ bin / sh 
 
 fmt ='
 ref =％（refname：short）
 
如果git merge-base --is-ancestor $ 1 $ ref;然后
 printf％s\\\
$ ref
 fi 
'
 
 eval$（git for-each-ref --shell  - format =$ fmtrefs / heads /）
  

在这个特别的例子中，我该如何避免使用 eval ？我已经查看了 Zenexer的回答中列出的选项，但是我找不到一个可行的方法。我正在寻找可移植的（跨越不同的shell）一个解决方案。

解决方案

code> eval ，你让 git for-each-ref 以一种容易处理的格式输出数据流。然后，你为这些数据编写一个定制处理器。

  git for-each-ref --format< values> \ 
＃更多选项
 refs / tags | while read refname object_type< more args> ;做
< code> 
完成
  

至于你给出的具体例子，这里是一个等价的非eval版本：

 ＃！/ bin / bash 
 
 if [$＃-ne 1];然后
 printfusage：git branchesthatcontain< rev> \\\
\\\

 exit 1 
 fi 
 
 rev = $ 1 
 
 git for-each-ref --format ='％（refname：short）'refs / heads \ 
 |同时阅读ref;做
如果git merge-base --is-ancestor$ rev$ ref;然后
 echo$ ref
 fi; 
完成
 
出口$？ 
  

我必须添加 git-for-each-ref 包含 - shell ， - python 和 - tcl code>标志确保数据正确转义：这与接受的答案中的情况不同到您引用的问题。

这个问题和相关答案也是相关的。

Most advanced uses of git for-each-ref that I've come across involve eval. For instance, the last example in the git-for-each-ref man page uses eval in order to execute the contents of the fmt variable:

#!/bin/sh

fmt='
    r=%(refname)
    # ... omitted, for conciseness ...
    '

eval=`git for-each-ref --shell --format="$fmt" \
    # ... omitted, for conciseness ...
    refs/tags`
eval "$eval"

However, the use of eval is associated with security risks; avoiding it, whenever possible, is considered good practice.

Here is a real example, adapted from this answer:

#!/bin/sh

fmt='
    ref=%(refname:short)

    if git merge-base --is-ancestor $1 $ref; then
      printf "%s\n" "$ref"
    fi
'

eval "$(git for-each-ref --shell --format="$fmt" refs/heads/)"

In this particular example, how can I avoid using eval? I've reviewed the options listed in Zenexer's answer, but I couldn't find one that does the trick. I'm looking for as portable (across different shells) a solution as possible.

解决方案

Instead of treating data as code using eval, you let git for-each-ref output a stream of data in a format that is easy for you to process. Then, you write a custom processor for that data.

git for-each-ref --format "<values>" \
     # more options
     refs/tags | while read refname object_type <more args> ; do
          <code>
     done

As for the specific example you gave, here is an equivalent non-eval version:

#!/bin/bash

if [ $# -ne 1 ]; then
    printf "usage: git branchesthatcontain <rev>\n\n"
    exit 1
fi

rev=$1

git for-each-ref --format='%(refname:short)' refs/heads \
    | while read ref; do 
          if git merge-base --is-ancestor "$rev" "$ref"; then
              echo "$ref"
          fi;
      done

exit $?

I must add that git-for-each-ref does include --shell, --python and --tcl flags which ensures that the data is properly escaped: this is not the same scenario as in the accepted answer to the question you reference.

This question and the associated answer are also relevant.

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