How do I check for valid Git branch names?

Question

I\'m developing a git post-receive hook in Python. Data is supplied on stdin with lines similar to

ef4d4037f8568e386629457d4d960915a85da2ae 61a4         


        

Answer 1

Let's dissect the various rules and build regex parts from them:

1. They can include slash / for hierarchical (directory) grouping, but no slash-separated component can begin with a dot . or end with the sequence .lock.

    # must not contain /.
    (?!.*/\.)
    # must not end with .lock
    (?

2. They must contain at least one /. This enforces the presence of a category like heads/, tags/ etc. but the actual names are not restricted. If the --allow-onelevel option is used, this rule is waived.

    .+/.+  # may get more precise later
   

3. They cannot have two consecutive dots .. anywhere.

    (?!.*\.\.)
   

4. They cannot have ASCII control characters (i.e. bytes whose values are lower than \040, or \177 DEL), space, tilde ~, caret ^, or colon : anywhere.

    [^\000-\037\177 ~^:]+   # pattern for allowed characters
   

5. They cannot have question-mark ?, asterisk *, or open bracket [ anywhere. See the --refspec-pattern option below for an exception to this rule.

    [^\000-\037\177 ~^:?*[]+   # new pattern for allowed characters
   

6. They cannot begin or end with a slash / or contain multiple consecutive slashes (see the --normalize option below for an exception to this rule)

    ^(?!/)
    (?

7. They cannot end with a dot ..

    (?

8. They cannot contain a sequence @{.

    (?!.*@\{)
   

9. They cannot contain a \.

    (?!.*\\)
   

Piecing it all together we arrive at the following monstrosity:

^(?!.*/\.)(?!.*\.\.)(?!/)(?!.*//)(?!.*@\{)(?!.*\\)[^\000-\037\177 ~^:?*[]+/[^\000-\037\177 ~^:?*[]+(?

And if you want to exclude those that start with build- then just add another lookahead:

^(?!build-)(?!.*/\.)(?!.*\.\.)(?!/)(?!.*//)(?!.*@\{)(?!.*\\)[^\000-\037\177 ~^:?*[]+/[^\000-\037\177 ~^:?*[]+(?

This can be optimized a bit as well by conflating a few things that look for common patterns:

^(?!@$|build-|/|.*([/.]\.|//|@\{|\\))[^\000-\037\177 ~^:?*[]+/[^\000-\037\177 ~^:?*[]+(?