* Question about fsck-objects output
@ 2007-01-25 18:22 Larry Streepy
2007-01-25 19:31 ` Shawn O. Pearce
2007-01-25 20:01 ` Linus Torvalds
0 siblings, 2 replies; 4+ messages in thread
From: Larry Streepy @ 2007-01-25 18:22 UTC (permalink / raw)
To: git
Sorry to ask such a basic question, but I can't quite decipher the output
of fsck-objects. When I run it, I get this:
git fsck-objects
dangling commit 2213f6d4dd39ca8baebd0427723723e63208521b
dangling commit f0d4e00196bd5ee54463e9ea7a0f0e8303da767f
dangling blob 6a6d0b01b3e96d49a8f2c7addd4ef8c3bd1f5761
Even after a "repack -a -d" they still exist. The man page has a short
explanation, but, at least for me, it wasn't fully enlightening. :-)
The man page says that dangling commits could be "root" commits, but since
my repo started as a clone of another repo, I don't see how I could have
any root commits. Also, the page doesn't really describe what a dangling
blob is.
So, can someone explain what these artifacts are and if they are a problem
that I should be worried about?
Thanks,
Larry.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Question about fsck-objects output
2007-01-25 18:22 Question about fsck-objects output Larry Streepy
@ 2007-01-25 19:31 ` Shawn O. Pearce
2007-01-25 20:01 ` Linus Torvalds
1 sibling, 0 replies; 4+ messages in thread
From: Shawn O. Pearce @ 2007-01-25 19:31 UTC (permalink / raw)
To: Larry Streepy; +Cc: git
Larry Streepy <larry@lightspeed.com> wrote:
> Sorry to ask such a basic question, but I can't quite decipher the output
> of fsck-objects. When I run it, I get this:
>
> git fsck-objects
> dangling commit 2213f6d4dd39ca8baebd0427723723e63208521b
> dangling commit f0d4e00196bd5ee54463e9ea7a0f0e8303da767f
> dangling blob 6a6d0b01b3e96d49a8f2c7addd4ef8c3bd1f5761
>
>
> Even after a "repack -a -d" they still exist. The man page has a short
> explanation, but, at least for me, it wasn't fully enlightening. :-)
>
> The man page says that dangling commits could be "root" commits, but since
> my repo started as a clone of another repo, I don't see how I could have
> any root commits. Also, the page doesn't really describe what a dangling
> blob is.
>
> So, can someone explain what these artifacts are and if they are a problem
> that I should be worried about?
These were probably created by amending a commit (`git commit --amend`).
Dangling commits simply mean no existing branch points at them,
either directly by a ref/tag or indirectly by the commit being
merged into them. They aren't part of any interesting history.
They could also be caused by deleting a branch before it was fully
merged into another branch. The commits and history are still
there, they just lack a name.
Dangling blobs mean the same thing; no existing branch uses
them in their revisions.
What most likely happened here was you committed a change, realized
it was slightly wrong, modified one file, then used `git commit
--amend -a` to update the commit with the correction. Later you
probably did the same thing, but only to correct the commit message.
The first instance caused the blob and commit to dangle, the
second caused another commit to dangle.
You can use `git show id` (where id is the commit id above) to see
what the commit actually is.
You can use `git prune` to have these objects deleted. For safety
reasons `repack -a -d` won't touch them. But they don't take up
a lot of disk space (usually) so pruning isn't something to be
too concerned about.
--
Shawn.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Question about fsck-objects output
2007-01-25 18:22 Question about fsck-objects output Larry Streepy
2007-01-25 19:31 ` Shawn O. Pearce
@ 2007-01-25 20:01 ` Linus Torvalds
2007-01-25 20:08 ` Larry Streepy
1 sibling, 1 reply; 4+ messages in thread
From: Linus Torvalds @ 2007-01-25 20:01 UTC (permalink / raw)
To: Larry Streepy; +Cc: git
[ Maybe this should be a FAQ answer in some git documentation? Feel free
to edit up this email and use it as a base.. ]
On Thu, 25 Jan 2007, Larry Streepy wrote:
> Sorry to ask such a basic question, but I can't quite decipher the output of
> fsck-objects. When I run it, I get this:
>
> git fsck-objects
> dangling commit 2213f6d4dd39ca8baebd0427723723e63208521b
> dangling commit f0d4e00196bd5ee54463e9ea7a0f0e8303da767f
> dangling blob 6a6d0b01b3e96d49a8f2c7addd4ef8c3bd1f5761
>
>
> Even after a "repack -a -d" they still exist. The man page has a short
> explanation, but, at least for me, it wasn't fully enlightening. :-)
>
> The man page says that dangling commits could be "root" commits, but since my
> repo started as a clone of another repo, I don't see how I could have any root
> commits. Also, the page doesn't really describe what a dangling blob is.
>
> So, can someone explain what these artifacts are and if they are a problem
> that I should be worried about?
The most common situation is that you've rebased a branch (or you have
pulled from somebody else who rebased a branch, like the "pu" branch in
the git.git archive itself).
What happens is that the old head of the original branch still exists, as
does obviously everything it pointed to. The branch pointer itself just
doesn't, since you replaced it with another one.
However, there are certainly other situations too that cause dangling
objects. For example, the "dangling blob" situation you have tends to be
because you did a "git add" of a file, but then, before you actually
committed it and made it part of the bigger picture, you changed something
else in that file and committed that *updated* thing - the old state that
you added originally ends up not being pointed to by any commit/tree, so
it's now a dangling blob object.
Similarly, when the "recursive" merge strategy runs, and finds that there
are criss-cross merges and thus more than one merge base (which is fairly
unusual, but it does happen), it will generate one temporary midway tree
(or possibly even more, if you had lots of criss-crossing merges and
more than two merge bases) as a temporary internal merge base, and again,
those are real objects, but the end result will not end up pointing to
them, so they end up "dangling" in your repository.
Generally, dangling objects aren't anything to worry about. They can even
be very useful: if you screw something up, the dangling objects can be how
you recover your old tree (say, you did a rebase, and realized that you
really didn't want to - you can look at what dangling objects you have,
and decide to reset your head to some old dangling state).
For commits, the most useful thing to do with dangling objects tends to be
to do a simple
gitk <dangling-commit-sha-goes-here> --not --all
which means exactly what it sounds like: it says that you want to see the
commit history that is described by the dangling commit(s), but you do NOT
want to see the history that is described by all your branches and tags
(which are the things you normally reach). That basically shows you in a
nice way what the danglign commit was (and notice that it might not be
just one commit: we only report the "tip of the line" as being dangling,
but there might be a whole deep and complex commit history that has gotten
dropped - rebasing will do that).
For blobs and trees, you can't do the same, but you can examine them. You
can just do
git show <dangling-blob/tree-sha-goes-here>
to show what the contents of the blob were (or, for a tree, basically what
the "ls" for that directory was), and that may give you some idea of what
the operation was that left that dangling object.
Usually, dangling blobs and trees aren't very interesting. They're almost
always the result of either being a half-way mergebase (the blob will
often even have the conflict markers from a merge in it, if you have had
conflicting merges that you fixed up by hand), or simply because you
interrupted a "git fetch" with ^C or something like that, leaving _some_
of the new objects in the object database, but just dangling and useless.
Anyway, once you are sure that you're not interested in any dangling
state, you can just prune all unreachable objects:
git prune
and they'll be gone. But you should only run "git prune" on a quiescent
repository - it's kind of like doing a filesystem fsck recovery: you don't
want to do that while the filesystem is mounted.
(The same is true of "git-fsck-objects" itself, btw - but since
git-fsck-objects never actually *changes* the repository, it just reports
on what it found, git-fsck-objects itself is never "dangerous" to run.
Running it while somebody is actually changing the repository can cause
confusing and scary messages, but it won't actually do anything bad. In
contrast, running "git prune" while somebody is actively changing the
repository is a *BAD* idea).
Linus
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Question about fsck-objects output
2007-01-25 20:01 ` Linus Torvalds
@ 2007-01-25 20:08 ` Larry Streepy
0 siblings, 0 replies; 4+ messages in thread
From: Larry Streepy @ 2007-01-25 20:08 UTC (permalink / raw)
To: Linus Torvalds; +Cc: git
[-- Attachment #1: Type: text/plain, Size: 5348 bytes --]
Excellent, I have done a rebase, so that could certainly be it. I'll
take a look at the contents using the suggestions you provided.
Thanks for the enlightenment. :-)
Larry.
Linus Torvalds wrote:
> [ Maybe this should be a FAQ answer in some git documentation? Feel free
> to edit up this email and use it as a base.. ]
>
> On Thu, 25 Jan 2007, Larry Streepy wrote:
>
>
>> Sorry to ask such a basic question, but I can't quite decipher the output of
>> fsck-objects. When I run it, I get this:
>>
>> git fsck-objects
>> dangling commit 2213f6d4dd39ca8baebd0427723723e63208521b
>> dangling commit f0d4e00196bd5ee54463e9ea7a0f0e8303da767f
>> dangling blob 6a6d0b01b3e96d49a8f2c7addd4ef8c3bd1f5761
>>
>>
>> Even after a "repack -a -d" they still exist. The man page has a short
>> explanation, but, at least for me, it wasn't fully enlightening. :-)
>>
>> The man page says that dangling commits could be "root" commits, but since my
>> repo started as a clone of another repo, I don't see how I could have any root
>> commits. Also, the page doesn't really describe what a dangling blob is.
>>
>> So, can someone explain what these artifacts are and if they are a problem
>> that I should be worried about?
>>
>
> The most common situation is that you've rebased a branch (or you have
> pulled from somebody else who rebased a branch, like the "pu" branch in
> the git.git archive itself).
>
> What happens is that the old head of the original branch still exists, as
> does obviously everything it pointed to. The branch pointer itself just
> doesn't, since you replaced it with another one.
>
> However, there are certainly other situations too that cause dangling
> objects. For example, the "dangling blob" situation you have tends to be
> because you did a "git add" of a file, but then, before you actually
> committed it and made it part of the bigger picture, you changed something
> else in that file and committed that *updated* thing - the old state that
> you added originally ends up not being pointed to by any commit/tree, so
> it's now a dangling blob object.
>
> Similarly, when the "recursive" merge strategy runs, and finds that there
> are criss-cross merges and thus more than one merge base (which is fairly
> unusual, but it does happen), it will generate one temporary midway tree
> (or possibly even more, if you had lots of criss-crossing merges and
> more than two merge bases) as a temporary internal merge base, and again,
> those are real objects, but the end result will not end up pointing to
> them, so they end up "dangling" in your repository.
>
> Generally, dangling objects aren't anything to worry about. They can even
> be very useful: if you screw something up, the dangling objects can be how
> you recover your old tree (say, you did a rebase, and realized that you
> really didn't want to - you can look at what dangling objects you have,
> and decide to reset your head to some old dangling state).
>
> For commits, the most useful thing to do with dangling objects tends to be
> to do a simple
>
> gitk <dangling-commit-sha-goes-here> --not --all
>
> which means exactly what it sounds like: it says that you want to see the
> commit history that is described by the dangling commit(s), but you do NOT
> want to see the history that is described by all your branches and tags
> (which are the things you normally reach). That basically shows you in a
> nice way what the danglign commit was (and notice that it might not be
> just one commit: we only report the "tip of the line" as being dangling,
> but there might be a whole deep and complex commit history that has gotten
> dropped - rebasing will do that).
>
> For blobs and trees, you can't do the same, but you can examine them. You
> can just do
>
> git show <dangling-blob/tree-sha-goes-here>
>
> to show what the contents of the blob were (or, for a tree, basically what
> the "ls" for that directory was), and that may give you some idea of what
> the operation was that left that dangling object.
>
> Usually, dangling blobs and trees aren't very interesting. They're almost
> always the result of either being a half-way mergebase (the blob will
> often even have the conflict markers from a merge in it, if you have had
> conflicting merges that you fixed up by hand), or simply because you
> interrupted a "git fetch" with ^C or something like that, leaving _some_
> of the new objects in the object database, but just dangling and useless.
>
> Anyway, once you are sure that you're not interested in any dangling
> state, you can just prune all unreachable objects:
>
> git prune
>
> and they'll be gone. But you should only run "git prune" on a quiescent
> repository - it's kind of like doing a filesystem fsck recovery: you don't
> want to do that while the filesystem is mounted.
>
> (The same is true of "git-fsck-objects" itself, btw - but since
> git-fsck-objects never actually *changes* the repository, it just reports
> on what it found, git-fsck-objects itself is never "dangerous" to run.
> Running it while somebody is actually changing the repository can cause
> confusing and scary messages, but it won't actually do anything bad. In
> contrast, running "git prune" while somebody is actively changing the
> repository is a *BAD* idea).
>
> Linus
>
[-- Attachment #2: larry.vcf --]
[-- Type: text/x-vcard, Size: 298 bytes --]
begin:vcard
fn:Larry Streepy
n:Streepy;Larry
org:Lightspeed Logic
adr;dom:Building 2, suite 130;;11612 Bee Caves Road;Austin;TX;78738
email;internet:larry@lightspeed.com
title:Sr. Staff Software Engineer
tel;work:408-616-3292
x-mozilla-html:TRUE
url:http://ww.lightspeed.com
version:2.1
end:vcard
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2007-01-25 20:06 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2007-01-25 18:22 Question about fsck-objects output Larry Streepy
2007-01-25 19:31 ` Shawn O. Pearce
2007-01-25 20:01 ` Linus Torvalds
2007-01-25 20:08 ` Larry Streepy
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).