The Git Store
#############

..  include::   /header.inc

Git_ stores everything needed to manage a project in a hidden **.git** subdirectory in
the root directory of your project. Normally, you never pay any attention to what is in that folder. However, we will be using a variant of the Git store for our literate programming work, so let's look inside a bit deeper.

Git Blobs
*********

Any time Git_ needs to store a version of a file, it runs that file's content
through a hash function to calculate a unique 40 character code for that
content. Git_ then breaks that hash code into twp parts: The first two
characters name a subdirectory under **.git/objects**, and the remaining 38
characters of the code become the file name for that content in the indicated
subdirectory. The actual content is stored in a compressed file.

Hers is example code that will generate the 40 character hash code for an input file:

..  code-block::    python

    import sys
    import hashlib

    BUF_SIZE = 65536

    sha1 = hashlib.sha1()

    with open(sys.argv[1], 'rb') as f:
        while True:
            data = f.read(BUF_SIZE)
            if not data:
                break
            sha1.update(data)

    print("SHA1: {0}".format(sha1.hexdigest())

Handling Indentation

..  code-block:: python

    def getIndentationCount(spaces):
        count = 0
        for ch in spaces:
            if ch == '\t':
                count += 8 - (count % 8)
            else:
                count += 1
        return count

Checking for new indent of dedent

..  code-block:: python

    indent = self.getIndentationCount(spaces)
    previous = self.indents[-1] if self.indents else 0
    self.emitToken(self.commonToken(self.NEWLINE, newLine, indent=indent))
    if indent == previous:
        self.skip()
    elif indent > previous:
        self.indents.append(indent)
        self.emitToken(self.commonToken(LanguageParser.INDENT, spaces))
    else:
        while self.indents and self.indents[-1] > indent:
            self.emitToken(self.createDedent())
            self.indents.pop()