hash-object is different from ruby's implemention

[jingsam]

In https://github.com/progit/progit2/blob/master/book/10-git-internals/sections/objects.asc#object-storage, we use ruby to hash what is up, doc? and we get:

bd9dbf5aae1a3862dd1526723246b20206e5fc37

However, I hash this string with hash-object, from which I got a different hash:

$ echo "what is up, doc?" | git hash-object --stdin -w
7108f7ecb345ee9d0084193f147cdad4d2998293
$ git cat-file -p 7108f7ecb345ee9d0084193f147cdad4d2998293
what is up, doc?

Test on:
macOS 10.13.5
git version 2.15.1 (Apple Git-101)
config:

[core]
	repositoryformatversion = 0
	filemode = true
	bare = false
	logallrefupdates = true
	ignorecase = true
	precomposeunicode = true

[krisfremen]

echo always appends a newline to its output.

use the -n flag to get the output without the trailing newline.

$ echo -n "what is up, doc?" | git hash-object --stdin -w
bd9dbf5aae1a3862dd1526723246b20206e5fc37

[jingsam]

Thanks a lot. I think it would be better to add a paragraph to state this issue. As in this chapter 0f Git object, I see:

$ echo "version 1" |  git hash-object --stdin -w
$ echo "version 2" |  git hash-object --stdin -w

That maybe cause confusion when readers try:

$ echo  "what is up, doc?" | git hash-object --stdin -w

[krisfremen]

Pull requests are welcome. :)