Re: [BUG] branch renamed to 'HEAD'

[Junio C Hamano]

Jacob Keller  writes:

> I didn't find any problems besides what you had already outlined
> before I started reading the series. It looks pretty much like I
> thought it would. I like the idea of saying "I want X" rather than the
> command returning "This was a Y"

Yeah, thanks for reading it through.  Except for one disambiguation
glitch Peff noticed himself, I found the entire series a pleasant
read.

Re: [BUG] branch renamed to 'HEAD'

[Jacob Keller]

On Tue, Feb 28, 2017 at 4:06 AM, Jeff King  wrote:
> On Mon, Feb 27, 2017 at 07:53:02PM -0500, Jeff King wrote:
>
>> On Mon, Feb 27, 2017 at 04:33:36PM -0800, Junio C Hamano wrote:
>>
>> > A flag to affect the behaviour (as opposed to  as a secondary
>> > return value, like Peff's patch does) can be made to work.  Perhaps
>> > a flag that says "keep the input as is if the result is not a local
>> > branch name" would pass an input "@" intact and that may be
>> > sufficient to allow "git branch -m @" to rename the current branch
>> > to "@" (I do not think it is a sensible rename, though ;-).  But
>> > probably some callers need to keep the original input and compare
>> > with the result to see if we expanded anything if we go that route.
>> > At that point, I am not sure if there are much differences in the
>> > ease of use between the two approaches.
>>
>> I just went into more detail in my reply to Jacob, but I do think this
>> is a workable approach (and fortunately we seem to have banned bare "@"
>> as a name, along with anything containing "@{}", so I think we would end
>> up rejecting these nonsense names).
>>
>> I'll see if I can work up a patch. We'll still need to pass the flag
>> around through the various functions, but at least it will be a flag and
>> not a confusing negated out-parameter.
>
> OK, I have a series which fixes this (diffstat below). When I audited
> the other callers of interpret_branch_name() and strbuf_branchname(), it
> turned out to be even more complicated. The callers basically fall into
> a few buckets:
>
>   1. Callers like get_sha1() and merge_name() pass the result to
>  dwim_ref(), and are prepared to handle anything.
>
>   2. Some callers stick "refs/heads/" in front of the result, and
>  obviously only want local names. Most of git-branch and
>  git-checkout fall into this boat.
>
>   3. "git branch -d" can delete local _or_ remote branches, depending on
>  the "-r" flag. So the expansion it wants varies, and we need to
>  handle "just local" or "just remote".
>
> So I converted the "only_branch" flag to an "allowed" bit-field. No
> callers actually ask for more than a single type at once, but it was
> easy to do it that way. It serves all of the callers, and will easily
> adapt for the future (e.g., if "git branch -a -d" were ever allowed).
>
>   [1/8]: interpret_branch_name: move docstring to header file
>   [2/8]: strbuf_branchname: drop return value
>   [3/8]: strbuf_branchname: add docstring
>   [4/8]: interpret_branch_name: allow callers to restrict expansions
>   [5/8]: t3204: test git-branch @-expansion corner cases
>   [6/8]: branch: restrict @-expansions when deleting
>   [7/8]: strbuf_check_ref_format(): expand only local branches
>   [8/8]: checkout: restrict @-expansions when finding branch
>
>  builtin/branch.c  |   5 +-
>  builtin/checkout.c|   2 +-
>  builtin/merge.c   |   2 +-
>  cache.h   |  32 -
>  refs.c|   2 +-
>  revision.c|   2 +-
>  sha1_name.c   |  76 ++---
>  strbuf.h  |  21 +-
>  t/t3204-branch-name-interpretation.sh | 122 
> ++
>  9 files changed, 220 insertions(+), 44 deletions(-)
>  create mode 100755 t/t3204-branch-name-interpretation.sh
>
> -Peff

I didn't find any problems besides what you had already outlined
before I started reading the series. It looks pretty much like I
thought it would. I like the idea of saying "I want X" rather than the
command returning "This was a Y"

Re: [BUG] branch renamed to 'HEAD'

[Jeff King]

On Mon, Feb 27, 2017 at 07:53:02PM -0500, Jeff King wrote:

> On Mon, Feb 27, 2017 at 04:33:36PM -0800, Junio C Hamano wrote:
> 
> > A flag to affect the behaviour (as opposed to  as a secondary
> > return value, like Peff's patch does) can be made to work.  Perhaps
> > a flag that says "keep the input as is if the result is not a local
> > branch name" would pass an input "@" intact and that may be
> > sufficient to allow "git branch -m @" to rename the current branch
> > to "@" (I do not think it is a sensible rename, though ;-).  But
> > probably some callers need to keep the original input and compare
> > with the result to see if we expanded anything if we go that route.
> > At that point, I am not sure if there are much differences in the
> > ease of use between the two approaches.
> 
> I just went into more detail in my reply to Jacob, but I do think this
> is a workable approach (and fortunately we seem to have banned bare "@"
> as a name, along with anything containing "@{}", so I think we would end
> up rejecting these nonsense names).
> 
> I'll see if I can work up a patch. We'll still need to pass the flag
> around through the various functions, but at least it will be a flag and
> not a confusing negated out-parameter.

OK, I have a series which fixes this (diffstat below). When I audited
the other callers of interpret_branch_name() and strbuf_branchname(), it
turned out to be even more complicated. The callers basically fall into
a few buckets:

  1. Callers like get_sha1() and merge_name() pass the result to
 dwim_ref(), and are prepared to handle anything.

  2. Some callers stick "refs/heads/" in front of the result, and
 obviously only want local names. Most of git-branch and
 git-checkout fall into this boat.

  3. "git branch -d" can delete local _or_ remote branches, depending on
 the "-r" flag. So the expansion it wants varies, and we need to
 handle "just local" or "just remote".

So I converted the "only_branch" flag to an "allowed" bit-field. No
callers actually ask for more than a single type at once, but it was
easy to do it that way. It serves all of the callers, and will easily
adapt for the future (e.g., if "git branch -a -d" were ever allowed).

  [1/8]: interpret_branch_name: move docstring to header file
  [2/8]: strbuf_branchname: drop return value
  [3/8]: strbuf_branchname: add docstring
  [4/8]: interpret_branch_name: allow callers to restrict expansions
  [5/8]: t3204: test git-branch @-expansion corner cases
  [6/8]: branch: restrict @-expansions when deleting
  [7/8]: strbuf_check_ref_format(): expand only local branches
  [8/8]: checkout: restrict @-expansions when finding branch

 builtin/branch.c  |   5 +-
 builtin/checkout.c|   2 +-
 builtin/merge.c   |   2 +-
 cache.h   |  32 -
 refs.c|   2 +-
 revision.c|   2 +-
 sha1_name.c   |  76 ++---
 strbuf.h  |  21 +-
 t/t3204-branch-name-interpretation.sh | 122 ++
 9 files changed, 220 insertions(+), 44 deletions(-)
 create mode 100755 t/t3204-branch-name-interpretation.sh

-Peff

Re: [BUG] branch renamed to 'HEAD'

[Jacob Keller]

On Mon, Feb 27, 2017 at 4:53 PM, Jeff King  wrote:
> On Mon, Feb 27, 2017 at 04:33:36PM -0800, Junio C Hamano wrote:
>
>> A flag to affect the behaviour (as opposed to  as a secondary
>> return value, like Peff's patch does) can be made to work.  Perhaps
>> a flag that says "keep the input as is if the result is not a local
>> branch name" would pass an input "@" intact and that may be
>> sufficient to allow "git branch -m @" to rename the current branch
>> to "@" (I do not think it is a sensible rename, though ;-).  But
>> probably some callers need to keep the original input and compare
>> with the result to see if we expanded anything if we go that route.
>> At that point, I am not sure if there are much differences in the
>> ease of use between the two approaches.
>
> I just went into more detail in my reply to Jacob, but I do think this
> is a workable approach (and fortunately we seem to have banned bare "@"
> as a name, along with anything containing "@{}", so I think we would end
> up rejecting these nonsense names).
>
> I'll see if I can work up a patch. We'll still need to pass the flag
> around through the various functions, but at least it will be a flag and
> not a confusing negated out-parameter.
>
> -Peff

Yes, this is pretty much what I had imagined. I look forward to seeing
the patch.

Thanks,
Jake

Re: [BUG] branch renamed to 'HEAD'

[Jeff King]

On Mon, Feb 27, 2017 at 04:33:36PM -0800, Junio C Hamano wrote:

> A flag to affect the behaviour (as opposed to  as a secondary
> return value, like Peff's patch does) can be made to work.  Perhaps
> a flag that says "keep the input as is if the result is not a local
> branch name" would pass an input "@" intact and that may be
> sufficient to allow "git branch -m @" to rename the current branch
> to "@" (I do not think it is a sensible rename, though ;-).  But
> probably some callers need to keep the original input and compare
> with the result to see if we expanded anything if we go that route.
> At that point, I am not sure if there are much differences in the
> ease of use between the two approaches.

I just went into more detail in my reply to Jacob, but I do think this
is a workable approach (and fortunately we seem to have banned bare "@"
as a name, along with anything containing "@{}", so I think we would end
up rejecting these nonsense names).

I'll see if I can work up a patch. We'll still need to pass the flag
around through the various functions, but at least it will be a flag and
not a confusing negated out-parameter.

-Peff

Re: [BUG] branch renamed to 'HEAD'

[Jacob Keller]

On Mon, Feb 27, 2017 at 2:28 PM, Junio C Hamano  wrote:
> Jeff King  writes:
>
>> I guess something like the patch below works, but I wonder if there is a
>> less-horrible way to accomplish the same thing.
>
> I suspect that a less-horrible would be a lot more intrusive.  It
> would go like "interpret-branch-name only gives local branch name,
> and when it does not show it, the callers that know they do not
> necessarily need local branch name would call other at-mark things".
> As you pointed out with the @{upstream} that potentially point at a
> local branch, it will quickly get more involved, I would think, and
> I tend to think that this patch of yours is probably the least evil
> one among possible solutions.
>
> Perhaps with s/not_in_refs_heads/not_a_branch_name/ (or swapping
> polarity, "is_a_branch_name"), the resulting code may not be too
> hard to read?
>
> Thanks.

What about changing interpret-branch-name gains a flag to return a
fully qualified ref rather than returning just the name? That seems
like it would be more reasonable behavior.

Thanks,
Jake

Re: [BUG] branch renamed to 'HEAD'

[Jeff King]

On Mon, Feb 27, 2017 at 03:05:37PM -0800, Jacob Keller wrote:

> > Perhaps with s/not_in_refs_heads/not_a_branch_name/ (or swapping
> > polarity, "is_a_branch_name"), the resulting code may not be too
> > hard to read?
> 
> What about changing interpret-branch-name gains a flag to return a
> fully qualified ref rather than returning just the name? That seems
> like it would be more reasonable behavior.

That's not sufficient. If I feed "refs/remotes/origin/master" as a
branch name to git-branch, then as silly as that is, it is the branch
whose ref is "refs/heads/refs/remotes/origin/master".

Since interpret_branch_name() is not fully qualifying everything, but
rather just _sometimes_ replace @-marks with refnames, we cannot tell
from just the string the difference between "the user fed us
refs/remotes/foo" and "the @-mark expanded to a non-branch
refs/remotes/foo". We need one extra bit of information to know whether
an expansion occurred.

You could give a flag that says "do not expand to anything outside of
refs/heads/" that would suppress the @->HEAD mark, as well as
@{upstream} when upstream is outside of refs/heads. That would certainly
be less nasty than the out-parameter, but I wasn't sure that the error
handling was what we wanted.

In strbuf_branchname(), we quietly turn that error into a "0", which
causes us to retain the original text. We then feed that into
check_refname_format() in strbuf_check_branch_ref(). Which I think would
complain, and you'd get "not a valid refname: @{upstream}". If we have
the out-bit, we can say "I understand what @{upstream} means, but it
does not expand to a local branch". That's a more specific error, but
maybe it is not worth the hassle to produce it.

-Peff

Re: [BUG] branch renamed to 'HEAD'

[Jeff King]

On Mon, Feb 27, 2017 at 02:28:09PM -0800, Junio C Hamano wrote:

> Jeff King  writes:
> 
> > I guess something like the patch below works, but I wonder if there is a
> > less-horrible way to accomplish the same thing.
> 
> I suspect that a less-horrible would be a lot more intrusive.  It
> would go like "interpret-branch-name only gives local branch name,
> and when it does not show it, the callers that know they do not
> necessarily need local branch name would call other at-mark things".
> As you pointed out with the @{upstream} that potentially point at a
> local branch, it will quickly get more involved, I would think, and
> I tend to think that this patch of yours is probably the least evil
> one among possible solutions.  
> 
> Perhaps with s/not_in_refs_heads/not_a_branch_name/ (or swapping
> polarity, "is_a_branch_name"), the resulting code may not be too
> hard to read?

I actually started with not_a_branch_name, but I wanted specifically to
talk about refs_heads, because we sometimes refer to remote-tracking
branches as "branches" (and the function is called interpret_branch_name(),
after all).

I agree it would be easier to read if the logic were flipped, but I'm
not sure that would be correct. The function knows when it has done a
replacement that takes us outside of a normal branch name. But when it
hasn't, it doesn't really know how the result should be interpreted.

For our purposes in this caller it is enough to say that "foo" should be
treated as "refs/heads/foo", but I don't think that is generally true of
interpret_branch_name(), which might be called as part of get_sha1().

So one alternative is to leave the logic the same way but try to give it
a better name. E.g., call it something like "replaced_with_non_branch"
or something. But there, another negation snuck in. The correct
non-negated thing is really "replaced_with_HEAD_or_refs_remotes" but
that is rather awkward.

-Peff

Re: [BUG] branch renamed to 'HEAD'

[Junio C Hamano]

Jacob Keller  writes:

> What about changing interpret-branch-name gains a flag to return a
> fully qualified ref rather than returning just the name? That seems
> like it would be more reasonable behavior.

There are two kinds of callers to i-b-n.  The ones that want a local
branch name because they are parsing special places on the command
line that using a local branch name makes difference (as opposed to
using any extended SHA-1 expression), like "git checkout master"
(which means different thing from "git checkout master^0").  And the
ones that can use any object name.

It depends on how your flag works, but if it means "add refs/heads/
when you got a local branch name", then that would not work well for
the former callers, as end-user inputs @{-1} and refs/heads/master
would become indistinguishable.  The former is expanded to 'master'
(if you were on that branch) and ends up being refs/heads/master.
"git checkout refs/heads/master" would be (unless you have a branch
with that name, i.e. refs/heads/refs/heads/master) a request to
detach HEAD at the commit, but the user wanted to be on the previous
branch.  And the latter iclass of callers are probably already happy
with or without the flag, so they won't be helped, either.

A flag to affect the behaviour (as opposed to  as a secondary
return value, like Peff's patch does) can be made to work.  Perhaps
a flag that says "keep the input as is if the result is not a local
branch name" would pass an input "@" intact and that may be
sufficient to allow "git branch -m @" to rename the current branch
to "@" (I do not think it is a sensible rename, though ;-).  But
probably some callers need to keep the original input and compare
with the result to see if we expanded anything if we go that route.
At that point, I am not sure if there are much differences in the
ease of use between the two approaches.

Re: [BUG] branch renamed to 'HEAD'

[Junio C Hamano]

Jeff King  writes:

> I guess something like the patch below works, but I wonder if there is a
> less-horrible way to accomplish the same thing.

I suspect that a less-horrible would be a lot more intrusive.  It
would go like "interpret-branch-name only gives local branch name,
and when it does not show it, the callers that know they do not
necessarily need local branch name would call other at-mark things".
As you pointed out with the @{upstream} that potentially point at a
local branch, it will quickly get more involved, I would think, and
I tend to think that this patch of yours is probably the least evil
one among possible solutions.  

Perhaps with s/not_in_refs_heads/not_a_branch_name/ (or swapping
polarity, "is_a_branch_name"), the resulting code may not be too
hard to read?

Thanks.

Re: [BUG] branch renamed to 'HEAD'

[Luc Van Oostenryck]

On Mon, Feb 27, 2017 at 04:02:33AM -0500, Jeff King wrote:
> Ugh. Actually, there are a few complications I found:
> 
>   1. Checking "HEAD" afterwards means you can't actually have a branch
>  named "HEAD". Doing so is probably insane, but we probably really
>  _do_ want to just disallow the @-conversion here.
> 
>   2. This isn't limited to just HEAD and @-conversion. For instance:

It's a bit what I was afraid of.

Luc

Re: [BUG] branch renamed to 'HEAD'

[Jeff King]

On Mon, Feb 27, 2017 at 03:01:58AM -0500, Jeff King wrote:

> I do think the bug is in strbuf_check_branch_ref(), but it's hard for it
> to do a better job. It needs to feed arbitrary expressions into
> interpret_branch_name() to resolve things like "@{upstream}", "@{-1}",
> "foo@{upstream}", etc.
> 
> The problem is that it expects a branch name to come out of
> interpret_branch_name(), which _mostly_ happens. The exception is HEAD,
> which is a "special" name. But the returned value doesn't indicate
> whether it is special or not.
> 
> My first thought was that we might be handling "@" in the wrong place.
> But it needs to happen here to make things like "@@{upstream}" work
> (which turns "@" into HEAD, and then finds its upstream).
> 
> So I think the options are:
> 
>   1. Before calling interpret_branch_name(), strbuf_check_branch_ref()
>  checks for "@". I don't like this because it's making assumptions
>  about how the result will be parsed and interpreted.
> 
>   2. interpret_branch_name() returns a flag that says "this isn't
>  _really_ a branch name".
> 
>   3. After interpret_branch_name() returns, check whether the result is
>  "HEAD".
> 
> Doing (2) is the "right" thing in the sense that the "is it a branch"
> logic remains with the matching parsing code. But we have to surface
> that value (maybe across recursion via reinterpret?). Since we're
> unlikely to ever grow a return value that matches this case except
> "HEAD", it might be simplest to just do (3).

Ugh. Actually, there are a few complications I found:

  1. Checking "HEAD" afterwards means you can't actually have a branch
 named "HEAD". Doing so is probably insane, but we probably really
 _do_ want to just disallow the @-conversion here.

  2. This isn't limited to just HEAD and @-conversion. For instance:

 $ git clone /some/repo tmp
 $ cd tmp
 $ git branch -m master @{upstream}
 $ git for-each-ref --format='%(refname)'
 refs/heads/origin/master
 refs/remotes/origin/HEAD
 refs/remotes/origin/master

 Er, what? Now we have a branch called origin/master.

So I think it probably is fundamentally wrong to be calling
interpret_branch_name() here at all, if we're just going to tack
"refs/heads/" in front of it. We don't know that we're getting out a
real branchname.

But we do still need to handle @{-1}. And I suppose it's even possible
that you could want to use foo@{upstream} as long as that upstream
points to a _local_ branch.

So perhaps the fundamental issue is that interpret_branch_name() does
not give us fully qualified refs in the return value. We don't have any
clue if the return value is in "refs/heads" or "refs/remotes", or what.
We can fix that, but we're still stuck comparing the result to see if it
starts with "refs/" or is just "HEAD".

Which is wrong. If the user fed us a branch name of "refs/remotes/foo",
then the correct branch name is "refs/heads/refs/remotes/foo" (as stupid
as that probably is). It's only the branch-reinterpretation that we need
to be careful of. So we really do need to somehow have
interpret_branch_name() tell us whether or not it found an actual
branch. Actually, it passes through unknown names, so it can only tell
us when it definitely found something _outside_ of refs/heads/.

I guess something like the patch below works, but I wonder if there is a
less-horrible way to accomplish the same thing.

diff --git a/cache.h b/cache.h
index 61fc86e6d..d52e24f4f 100644
--- a/cache.h
+++ b/cache.h
@@ -1319,7 +1319,8 @@ extern char *oid_to_hex_r(char *out, const struct 
object_id *oid);
 extern char *sha1_to_hex(const unsigned char *sha1);   /* static buffer 
result! */
 extern char *oid_to_hex(const struct object_id *oid);  /* same static buffer 
as sha1_to_hex */
 
-extern int interpret_branch_name(const char *str, int len, struct strbuf *);
+extern int interpret_branch_name(const char *str, int len, struct strbuf *,
+int *not_in_refs_heads);
 extern int get_oid_mb(const char *str, struct object_id *oid);
 
 extern int validate_headref(const char *ref);
diff --git a/refs.c b/refs.c
index cd36b64ed..78b32dd22 100644
--- a/refs.c
+++ b/refs.c
@@ -404,7 +404,7 @@ int refname_match(const char *abbrev_name, const char 
*full_name)
 static char *substitute_branch_name(const char **string, int *len)
 {
struct strbuf buf = STRBUF_INIT;
-   int ret = interpret_branch_name(*string, *len, );
+   int ret = interpret_branch_name(*string, *len, , NULL);
 
if (ret == *len) {
size_t size;
diff --git a/revision.c b/revision.c
index b37dbec37..233764802 100644
--- a/revision.c
+++ b/revision.c
@@ -147,7 +147,7 @@ static void add_pending_object_with_path(struct rev_info 
*revs,
revs->no_walk = 0;
if (revs->reflog_info && obj->type == OBJ_COMMIT) {
struct strbuf buf = STRBUF_INIT;
-   int len = interpret_branch_name(name, 0, );
+   int 

Re: [BUG] branch renamed to 'HEAD'

[Jeff King]

On Mon, Feb 27, 2017 at 11:43:46AM +0530, Karthik Nayak wrote:

> On Mon, Feb 27, 2017 at 10:22 AM, Luc Van Oostenryck
>  wrote:
> > Hi,
> >
> > I just discover something which very much seems a bug to me
> > while making an error in renaming a branch.
> > The scenario is the following:
> > - I have a branch named 'orig'
> > - I want to make some experimental changes on it:
> > $ git checkout -b temp orig
> > $ ... edit some files ...
> > $ ... make some tests & commits ...
> > - I'm happy with my changes, so I want to have my original
> >   branch to now points to the head of this temp branch
> >   but did it wrongly:
> > $ git branch -m -f orig @
> 
> Here you are using the '-m' flag, which is to rename a branch. So what
> you're essentially
> doing is:
> $ git branch -m -f orig HEAD
> Do note that this won't reset 'orig' to point to 'HEAD', rather this
> renames 'orig' to 'HEAD'.
> 
> What you actually want to do (to reset 'orig' to 'HEAD') is:
> $ git branch -f orig @
> This would make orig point to the current HEAD.

Regardless of the original intent, I think it is wrong to convert "@" to
a branch named "HEAD". I think the bug is in strbuf_check_branch_ref(),
which blindly sticks "refs/heads/" in front of any value we get from
interpret_branch_name(), which clearly does not make sense for HEAD.

-Peff

Re: [BUG] branch renamed to 'HEAD'

[Jeff King]

On Mon, Feb 27, 2017 at 02:49:15AM -0500, Jeff King wrote:

> > > $ git branch -m -f orig @
> [...]
> 
> Regardless of the original intent, I think it is wrong to convert "@" to
> a branch named "HEAD". I think the bug is in strbuf_check_branch_ref(),
> which blindly sticks "refs/heads/" in front of any value we get from
> interpret_branch_name(), which clearly does not make sense for HEAD.

I do think the bug is in strbuf_check_branch_ref(), but it's hard for it
to do a better job. It needs to feed arbitrary expressions into
interpret_branch_name() to resolve things like "@{upstream}", "@{-1}",
"foo@{upstream}", etc.

The problem is that it expects a branch name to come out of
interpret_branch_name(), which _mostly_ happens. The exception is HEAD,
which is a "special" name. But the returned value doesn't indicate
whether it is special or not.

My first thought was that we might be handling "@" in the wrong place.
But it needs to happen here to make things like "@@{upstream}" work
(which turns "@" into HEAD, and then finds its upstream).

So I think the options are:

  1. Before calling interpret_branch_name(), strbuf_check_branch_ref()
 checks for "@". I don't like this because it's making assumptions
 about how the result will be parsed and interpreted.

  2. interpret_branch_name() returns a flag that says "this isn't
 _really_ a branch name".

  3. After interpret_branch_name() returns, check whether the result is
 "HEAD".

Doing (2) is the "right" thing in the sense that the "is it a branch"
logic remains with the matching parsing code. But we have to surface
that value (maybe across recursion via reinterpret?). Since we're
unlikely to ever grow a return value that matches this case except
"HEAD", it might be simplest to just do (3).

-Peff

Re: [BUG] branch renamed to 'HEAD'

[Luc Van Oostenryck]

On Mon, Feb 27, 2017 at 11:43:46AM +0530, Karthik Nayak wrote:
> Hello,
> 
> Thanks for reporting, but I don't think it is a bug.
> 
> On Mon, Feb 27, 2017 at 10:22 AM, Luc Van Oostenryck
>  wrote:
> > Hi,
> >
> > I just discover something which very much seems a bug to me
> > while making an error in renaming a branch.
> > The scenario is the following:
> > - I have a branch named 'orig'
> > - I want to make some experimental changes on it:
> > $ git checkout -b temp orig
> > $ ... edit some files ...
> > $ ... make some tests & commits ...
> > - I'm happy with my changes, so I want to have my original
> >   branch to now points to the head of this temp branch
> >   but did it wrongly:
> > $ git branch -m -f orig @
> 
> Here you are using the '-m' flag, which is to rename a branch. So what
> you're essentially
> doing is:
> $ git branch -m -f orig HEAD
> Do note that this won't reset 'orig' to point to 'HEAD', rather this
> renames 'orig' to 'HEAD'.
> 
> What you actually want to do (to reset 'orig' to 'HEAD') is:
> $ git branch -f orig @
> This would make orig point to the current HEAD.

Sure. I said it the description that I made an error in the renaming.

What I consider as a bug is that '@', which stands for refs/HEAD,
have been interpreted as a branch named 'HEAD' and thus created a
reference refs/heads/HEAD.

Luc

Re: [BUG] branch renamed to 'HEAD'

[Karthik Nayak]

Hello,

Thanks for reporting, but I don't think it is a bug.

On Mon, Feb 27, 2017 at 10:22 AM, Luc Van Oostenryck
 wrote:
> Hi,
>
> I just discover something which very much seems a bug to me
> while making an error in renaming a branch.
> The scenario is the following:
> - I have a branch named 'orig'
> - I want to make some experimental changes on it:
> $ git checkout -b temp orig
> $ ... edit some files ...
> $ ... make some tests & commits ...
> - I'm happy with my changes, so I want to have my original
>   branch to now points to the head of this temp branch
>   but did it wrongly:
> $ git branch -m -f orig @

Here you are using the '-m' flag, which is to rename a branch. So what
you're essentially
doing is:
$ git branch -m -f orig HEAD
Do note that this won't reset 'orig' to point to 'HEAD', rather this
renames 'orig' to 'HEAD'.

What you actually want to do (to reset 'orig' to 'HEAD') is:
$ git branch -f orig @
This would make orig point to the current HEAD.

-- 
Regards,
Karthik Nayak

[BUG] branch renamed to 'HEAD'

[Luc Van Oostenryck]

Hi,

I just discover something which very much seems a bug to me
while making an error in renaming a branch.
The scenario is the following:
- I have a branch named 'orig'
- I want to make some experimental changes on it:
$ git checkout -b temp orig
$ ... edit some files ...
$ ... make some tests & commits ...
- I'm happy with my changes, so I want to have my original
  branch to now points to the head of this temp branch
  but did it wrongly:
$ git branch -m -f orig @
- Now I discover that I don't have anymore a branch named 'orig'
  That's fine, I made an error.
- I'm searching what had happened and discover the name my branch 
  have been renamed to: 'HEAD'
  In others words I have now an entry .git/refs/heads/HEAD
  which points to where my original branch pointed.

In my opinion, it's a bug that '@' have been expanded/resolved
into a branch named 'HEAD'.


Luc Van Oostenryck