Patterns

The pattern language used by gitmatch is intended to match that of Git’s gitignore(5) as of v2.36.1, including the undocumented features (mainly involving character classes) present in Git’s code.

Specifically:

• A pattern that starts with a # or is empty (after stripping trailing whitespace, a trailing /, and an initial !) is discarded

• Trailing space and tab characters in a pattern are stripped unless they are escaped with a backslash (which must itself not be escaped by another backslash)

• The forward slash (/) is used as the directory separator, even on Windows

• An initial ! negates the pattern; if a path matches a negated pattern, then any matches against previous patterns in the pattern list will be discarded.

• ? matches any character other than /

• * matches zero or more of any character other than /

• A leading or medial / anchors the pattern to the start of the path; if no such / is present, the pattern will match any path in which it is preceded by zero or more /-separated path components, each one composed of one or more non-/ characters

• A trailing / causes the pattern to only match directories

• An initial **/ matches zero or more /-separated path components

• A trailing /** matches one or more /-separated path components

• /**/ matches zero or more intervening /-separated path components; e.g., foo/**/bar matches foo/bar, foo/gnusto/bar, foo/gnusto/cleesh/bar, etc, but not fooxbar. Any following **/ (e.g., as in foo/**/**/**/bar) are redundant.

• ** in any other context is the same as *

• [ starts a character class, which must be terminated by ]. A character class will match any one character from the set of characters specified within. Characters can be specified as either themselves (e.g., [abc] matches a, b, or c) and/or as ranges (e.g., [a-f] matches any letter from a through f).

  • A character class can be inverted (making it match any character except those specified) by inserting ! or ^ after the opening [

  • A ] can be included in a character set by either escaping it or by placing it immediately after the opening [ and optional !/^.

    • In order for a ] to be used on the right side of a range, it must be escaped with a backslash; otherwise, it indicates the end of the character class, and the preceding hyphen and character before it will be treated literally rather than as a range.

  • Within a character class, an occurrence of [:PROPERTY:] will cause the class to include the ASCII characters with the given property; supported properties are:

    • alnum — letters and numbers

    • alpha — letters

    • blank — space and tab character

    • cntrl — any character with an ASCII value less than 0x20, plus the DEL (0x7F) character

    • digit — numbers

    • graph — letters, numbers, and punctuation

    • lower — lowercase letters

    • print — letters, numbers, punctuation, and the space character

    • punct — punctuation

    • space — space character, tab, line feed, and carriage return

    • upper — uppercase letters

    • xdigit — hexadecimal digits

    An unknown PROPERTY produces an invalid pattern that will not match anything.

  • A character class will never match a /

• Any character (special or not) in a pattern may be deprived of any special meaning by preceding it with a backslash. A backslash that is not followed by a character (after stripping a final /) produces an invalid pattern that will not match anything.

• If a parent directory of a given path matches a pattern list, then the given path (and the paths of all other files & directories recursively within the matching parent) will match the list as well, regardless of any negative patterns that may be present

• Patterns cannot contain the NUL character

• A path containing a NUL character will never match any pattern

• A pattern will never match the current directory

Strings vs. Bytes

While it’s usual in Python to work with str values of Unicode characters, Git instead operates on bytes. As a result, if a path or pattern contains non-ASCII characters, you may get different results using strs with gitmatch than you would with Git. For example, in Git, a file named “tést” will not be matched by the gitignore pattern t?st, because the é is encoded using more than one byte (assuming UTF-8), but if you pass these strings to gitmatch, the path will match (assuming the é is in composed form, which is a whole other can of worms). If you want Git’s behavior exactly, pass bytes to gitmatch instead of str (ideally encoded using os.fsencode()).

Note that the patterns passed to a single call to gitmatch.compile() must be either all str or all bytes, and a Gitignore instance constructed from str patterns can only match against str paths, while one constructed from bytes patterns can only match against bytes paths. (For the record, the pathlib classes count as str paths.)