Git - why are double dashes needed when running a command on a deleted file?

Question

Consider a git repository, where a file was once deleted.

git rm path/to/file
git commit -a -m\"testing\"

Ok, now I want to see the g

Answer 1

git log could be used on files as well as on branches, tags and so on.

Assume you have a folder called a/b/c, you'll get the commits for this folder using

git log a/b/c

That's fine.

You could also have a branch called d/e/f. You'll get the commits for this branch using

git log d/e/f

That's fine too.

Things start to get complicated if the item where git log should work on could not be clearly determined. If you're stupid and call your branch a/b/c too, git has no clue whose log shall be printed: that of the branch a/b/c or the log of your directory a/b/c? Therefore, you have to tell a bit more about the information you want to receive:

• show the log of the branch a/b/c:
  git log a/b/c --
• show the log of the folder a/b/c in the current branch:
  git log -- a/b/c
• show the log of the folder a/b/c in the a/b/c branch:
  git log a/b/c -- a/b/c

With the deleted file, you have a similar problem: there's neither a file called path/to/file present in the working copy, nor is there a branch called path/to/file. This is the reason why you have to specify what you want.

Of course, git could know that there was a file called path/to/file 20.000 revisions ago but this would require (worst case) to search the entire history of your project whether such a file existed or not.

By explicitly specifying the file path after the --, you tell git:

search harder for that file, even if it takes hours

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Conclusion (answering your question):
in your case, the -- is needed because otherwise git log would work slower in general.