Question

I would like to remove all changes to my working copy.
Running git status shows files modified.
Nothing I do seems to remove these modifications.
E.g.:

rbellamy@PROMETHEUS /d/Development/rhino-etl (master)
$ git status
# On branch master
# Changed but not updated:
#   (use "git add <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#       modified:   Rhino.Etl.Core/Enumerables/CachingEnumerable.cs
#       modified:   Rhino.Etl.Core/Pipelines/SingleThreadedPipelineExecuter.cs
#       modified:   Rhino.Etl.Tests/Rhino.Etl.Tests.csproj
#       modified:   Rhino.Etl.Tests/SingleThreadedPipelineExecuterTest.cs
#
no changes added to commit (use "git add" and/or "git commit -a")

rbellamy@PROMETHEUS /d/Development/rhino-etl (master)
$ git checkout -- Rhino.Etl.Core/Enumerables/CachingEnumerable.cs

rbellamy@PROMETHEUS /d/Development/rhino-etl (master)
$ git status
# On branch master
# Changed but not updated:
#   (use "git add <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#       modified:   Rhino.Etl.Core/Enumerables/CachingEnumerable.cs
#       modified:   Rhino.Etl.Core/Pipelines/SingleThreadedPipelineExecuter.cs
#       modified:   Rhino.Etl.Tests/Rhino.Etl.Tests.csproj
#       modified:   Rhino.Etl.Tests/SingleThreadedPipelineExecuterTest.cs
#
no changes added to commit (use "git add" and/or "git commit -a")

rbellamy@PROMETHEUS /d/Development/rhino-etl (master)
$ git checkout `git ls-files -m`

rbellamy@PROMETHEUS /d/Development/rhino-etl (master)
$ git status
# On branch master
# Changed but not updated:
#   (use "git add <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#       modified:   Rhino.Etl.Core/Enumerables/CachingEnumerable.cs
#       modified:   Rhino.Etl.Core/Pipelines/SingleThreadedPipelineExecuter.cs
#       modified:   Rhino.Etl.Tests/Rhino.Etl.Tests.csproj
#       modified:   Rhino.Etl.Tests/SingleThreadedPipelineExecuterTest.cs
#
no changes added to commit (use "git add" and/or "git commit -a")

rbellamy@PROMETHEUS /d/Development/rhino-etl (master)
$ git reset --hard HEAD
HEAD is now at 6c857e7 boo libraries updated to 2.0.9.2 and rhino.dsl.dll updated.

rbellamy@PROMETHEUS /d/Development/rhino-etl (master)
$ git status
# On branch master
# Changed but not updated:
#   (use "git add <file>..." to update what will be committed)
#   (use "git checkout -- <file>..." to discard changes in working directory)
#
#       modified:   Rhino.Etl.Core/Enumerables/CachingEnumerable.cs
#       modified:   Rhino.Etl.Core/Pipelines/SingleThreadedPipelineExecuter.cs
#       modified:   Rhino.Etl.Tests/Rhino.Etl.Tests.csproj
#       modified:   Rhino.Etl.Tests/SingleThreadedPipelineExecuterTest.cs
#
no changes added to commit (use "git add" and/or "git commit -a")

Answer 1

There are multiple problems that can cause this behaviour:

Line ending normalization

I’ve had these kinds of problems too. It comes down to git automatically converting crlf to lf. This is typically caused by mixed line endings in a single file. The file gets normalized in the index, but when git then denormalizes it again to diff it against the file in the working tree, the result is different.

But if you want to fix this, you should disable core.autocrlf, change all line endings to lf, and then enable it again. Or you can disable it altogether by doing:

git config --global core.autocrlf false

Instead of core.autocrlf, you can also consider using .gitattributes files. This way, you can make sure everyone using the repo uses the same normalization rules, preventing mixed line endings getting into the repository.

Also consider setting core.safecrlf to warn if you want git to warn you when a non-reversible normalization would be performed.

The git manpages say this:

CRLF conversion bears a slight chance
of corrupting data. autocrlf=true will
convert CRLF to LF during commit and
LF to CRLF during checkout. A file
that contains a mixture of LF and CRLF
before the commit cannot be recreated
by git. For text files this is the
right thing to do: it corrects line
endings such that we have only LF line
endings in the repository. But for
binary files that are accidentally
classified as text the conversion can
corrupt data.

Case-insensitive file systems

On case-insensitive filesystems, when the same filename with different casing is in the repository, git tries to checkout both, but only one ends up on the file system. When git tries to compare the second one, it would compare it to the wrong file.

The solution would either be switching to a non-case insensitive filesystem, but this in most cases is not feasible or renaming and committing one of the files on another filesystem.