Re: Fwd: diff not finding difference

From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Sep 25, 2015, 10:11 UTC
Message-ID: <8abeb16d123a602ee11dab3f93dab51e@dscho.org>
In-Reply-To: <CAKepmajegSMO91YZOe+P_BH2kzzR=RMqCE94XRQSfZzOVYKt6A@mail.gmail.com>

Hi Jack Adrian,

On 2015-09-24 23:09, Jack Adrian Zappa wrote:

Show 29 quoted lines

> This is a weird one:
> 
> [file-1 begin]
> 
> abcd efg hijklmnop
> 
> [file-1 end]
> 
> [file-2 begin]
> 
> blah blah blah
> /////////////////////////////////////////////////////////////////////////////////
> abdc boo ya!
> 
> [file-2 end]
> 
> Do a diff between these and it won't find any difference.
> 
> Same with the following two lines, each in a different file:
> sabc fed ghi jkl
> abc def ghi jkl
> 
> I first noticed this on the command line git and then in VS2013.  The
> original problem was like my first example.  The files were much
> longer, but all that git would see is the addition of the line of
> ////..., but not the removal of the original line.
> 
> I've tried some other simple file changes with similar results.
> Something seems to be definitely broken in git diff. :(

You might want to show your exact command-line invocation, i.e. the full information. I suspect that you missed the fact that `git diff a b` does not compare the file a to the file b, but instead it compares both a and b to what is recorded in the index. With one quirk: if the files a and b are not even recorded in the index, `git diff` will output nothing.

Now, the really confusing part for you was probably that your `file-2` *was* recorded in the index (maybe you made a backup copy with the extra file extension `.bak` or some such, and then called `git diff my-file.bak my-file` where `my-file` *actually is tracked by Git* but `my-file.bak` is not).

But `git diff` has so nice features that I wanted to use it myself to compare files or directories. That is why I introduced the `--no-index` option, years ago. And so I suspect that you called

    git diff file-1 file-2

when you actually wanted to call

    git diff --no-index file-1 file-2

Here is my shell session to verify that `git diff` works as designed:

``` me@work $ cat >file-1

abcd efg hijklmnop

me@work $ cat >file-2

blah blah blah ///////////////////////////////////////////////////////////////////////////////// abdc boo ya!

me@work $ git diff --no-index file-1 file-2

diff --git a/file-1 b/file-2
index 80ea2bc..f7fd7eb 100644
--- a/file-1
+++ b/file-2
@@ -1,3 +1,5 @@

-abcd efg hijklmnop
+blah blah blah
+/////////////////////////////////////////////////////////////////////////////////
+abdc boo ya!

me@work $
```

Please note that I ended the file contents for both `cat` calls [*1*] with a `Ctrl+D` which you cannot see in the pasted lines.

Ciao,
Johannes

Footnote *1*: Can you believe that I wanted to make that pun for at least ten years now?