Recommend git-filter-repo instead of git-filter-branch

filter-branch suffers from a deluge of disguised dangers that disfigure
history rewrites (i.e. deviate from the deliberate changes).  Many of
these problems are unobtrusive and can easily go undiscovered until the
new repository is in use.  This can result in problems ranging from an
even messier history than what led folks to filter-branch in the first
place, to data loss or corruption.  These issues cannot be backward
compatibly fixed, so add a warning to both filter-branch and its manpage
recommending that another tool (such as filter-repo) be used instead.

Also, update other manpages that referenced filter-branch.  Several of
these needed updates even if we could continue recommending
filter-branch, either due to implying that something was unique to
filter-branch when it applied more generally to all history rewriting
tools (e.g. BFG, reposurgeon, fast-import, filter-repo), or because
something about filter-branch was used as an example despite other more
commonly known examples now existing.  Reword these sections to fix
these issues and to avoid recommending filter-branch.

Finally, remove the section explaining BFG Repo Cleaner as an
alternative to filter-branch.  I feel somewhat bad about this,
especially since I feel like I learned so much from BFG that I put to
good use in filter-repo (which is much more than I can say for
filter-branch), but keeping that section presented a few problems:
  * In order to recommend that people quit using filter-branch, we need
    to provide them a recomendation for something else to use that
    can handle all the same types of rewrites.  To my knowledge,
    filter-repo is the only such tool.  So it needs to be mentioned.
  * I don't want to give conflicting recommendations to users
  * If we recommend two tools, we shouldn't expect users to learn both
    and pick which one to use; we should explain which problems one
    can solve that the other can't or when one is much faster than
    the other.
  * BFG and filter-repo have similar performance
  * All filtering types that BFG can do, filter-repo can also do.  In
    fact, filter-repo comes with a reimplementation of BFG named
    bfg-ish which provides the same user-interface as BFG but with
    several bugfixes and new features that are hard to implement in
    BFG due to its technical underpinnings.
While I could still mention both tools, it seems like I would need to
provide some kind of comparison and I would ultimately just say that
filter-repo can do everything BFG can, so ultimately it seems that it
is just better to remove that section altogether.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 8 insertions, 9 deletions

diff --git a/Documentation/git-gc.txt b/Documentation/git-gc.txt
index 247f765604..0c114ad1ca 100644
--- a/Documentation/git-gc.txt
+++ b/Documentation/git-gc.txt
@@ -115,15 +115,14 @@ NOTES
 -----
 
 'git gc' tries very hard not to delete objects that are referenced
-anywhere in your repository. In
-particular, it will keep not only objects referenced by your current set
-of branches and tags, but also objects referenced by the index,
-remote-tracking branches, refs saved by 'git filter-branch' in
-refs/original/, reflogs (which may reference commits in branches
-that were later amended or rewound), and anything else in the refs/* namespace.
-If you are expecting some objects to be deleted and they aren't, check
-all of those locations and decide whether it makes sense in your case to
-remove those references.
+anywhere in your repository. In particular, it will keep not only
+objects referenced by your current set of branches and tags, but also
+objects referenced by the index, remote-tracking branches, notes saved
+by 'git notes' under refs/notes/, reflogs (which may reference commits
+in branches that were later amended or rewound), and anything else in
+the refs/* namespace.  If you are expecting some objects to be deleted
+and they aren't, check all of those locations and decide whether it
+makes sense in your case to remove those references.
 
 On the other hand, when 'git gc' runs concurrently with another process,
 there is a risk of it deleting an object that the other process is using