Rebase, without ignoring, commits the same text changes?

The page mask git rebase

reads:

If <upstream>

not specified, the upstream parameters configured in parameters branch.<name>.remote

and will be used branch.<name>.merge

;

[....]

The entries that were previously saved to the temporary area are then overwritten to the current branch in order. Note that any commits in HEAD

that introduce the same textual changes as commit in HEAD..<upstream>

are skipped (i.e. a patch already accepted upstream with a different commit message or timestamp will be skipped).

Indeed, when I call git rebase master

and master

there is a commit with the same text changes as in my local branch history, it is ignored. However, I found that when I call git rebase

without specifying <upstream>

(which is by default master

), the output git rebase

seems to show that the same commit is not being ignored.

Example

Here's an example to demonstrate this. Here is the git history:

A---B master
 \
  B' topic

      

        
        
        
      

    

B

and B'

introduce the same text changes but have different commit messages. topic

configured for tracking master

.

First, I reinstall topic

on feed <upstream>

:

$ git checkout topic
$ git rebase master
First, rewinding head to replay your work on top of it...

      

        
        
        
      

    

Nothing happens as expected because B

both B'

are identical to each other.

However, if I omit <upstream>

:

$ git checkout topic
$ git rebase
First, rewinding head to replay your work on top of it...
Applying: Branch: topic
Using index info to reconstruct a base tree...
Falling back to patching base and 3-way merge...
No changes -- Patch already applied.

      

        
        
        
      

    

It seems that git doesn't skip B'

in the second output. Can anyone explain this discrepancy?

(I am using git version 1.9.4)