John Cai [off-list ref] writes:
It seems like this bug can be generalized to “git name-rev
--stdin” does not work with --no-undefined nor --name-only
The --name-only case seems clear to me that we should fix
it. It’s misleading to return the sha instead of “undefined”
for a rev without a symbolic name, as a sha could be a symbolic
name.
I think we can also make the argument that --no-undefined should
also die in --stdin mode when given a rev without any symbolic
names.
Hmph, the manual page documents:
--stdin::
Transform stdin by substituting all the 40-character SHA-1
hexes (say $hex) with "$hex ($rev_name)". When used with
--name-only, substitute with "$rev_name", omitting $hex
altogether. Intended for the scripter's use.
It is unfortunate that the way this option works is confusingly a
bit different from what we learned to expect from the --stdin option
other subcommands like "git pack-objects --stdin" takes. In short,
these are not equivalent:
git name-rev [<options>] $string
printf "%s" "$string" | xargs git name-rev [<options>]
printf "%s" "$string" | git name-rev --stdin [<options>]
The first two are supposed to be the equivalent, but the third one
is different by design. Its `--stdin` mode is expected to read
something like this [*]:
$ cat sample.txt
A revision that exists 2ae0a9cb82 is shown here,
and its full name is 2ae0a9cb8298185a94e5998086f380a355dd8907
while its tree object is 70d105cc79e63b81cfdcb08a15297c23e60b07ad
which probably is undescribable hexdigits.
and its designed use is to annotate its input into a more reader
friendly from with refnames where possible. Here is what we get:
$ git name-rev --stdin <sample.txt
A revision that exists 2ae0a9cb82 is shown here,
and its full name is 2ae0a9cb8298185a94e5998086f380a355dd8907 (master)
while its tree object is 70d105cc79e63b81cfdcb08a15297c23e60b07ad
which probably is undescribable hexdigits.
I notice a few things.
* An abbreviated commit object name is not affected;
* A 40-digit string that cannot be described with a reference is
left alone, without "undefined".
It might be debatable that the latter may want to be annotated with
"undefined", but as the command does not molest other noise strings
like "its" "full" name" in the input, I think the current behaviour
is preferred over appending "(undefined)" after a string we do not
recognize that happens to be 40-hex.
When used with --name-only, we see this:
$ git name-rev --name-only --stdin <sample.txt
A revision that exists 2ae0a9cb82 is shown here,
and its full name is master
while its tree object is 70d105cc79e63b81cfdcb08a15297c23e60b07ad
which probably is undescribable hexdigits.
So, as far as I can see, it is working as described. If there is
any bug in the things I saw and shown here, it is that it is
misleading to claim that this behaviour is intended for scripter's
use. It clearly is not scripter friendly when you want to run
"name-rev" on unbounded number of object names you have, which may
not fit on the command line, as that is not how it was designed to
be used.
Two possible things we can do to improve are
* Fix the documentation; it is not for scripters but for annotating
text with object names.
* Possibly add --names-from-standard-input option that would behave
more like "we cannot afford to stuff all object names on the
command line, so we feed them one by one from the standard input"
mode the "--stdin" option of other subcommands use.
I do not think the latter is so important, as it is perfectly OK to
use xargs to split the large input into multiple invocations of
name-rev. This is unlike "pack-objects --stdin" where the command
needs to see _all_ input in a single invocation.
[Footnote]
* The sample input was produced with
$ cat >sample.txt <<EOF
A revision that exists $(git rev-parse --short HEAD) is shown here,
and its full name is $(git rev-parse HEAD)
while its tree object is $(git rev-parse HEAD:)
which probably is undescribable hexdigits.
EOF
if you want to try it at home ;-)
On Dec 24, 2021, at 11:42 AM, Junio C Hamano [off-list ref] wrote:
John Cai [off-list ref] writes:
quoted
It seems like this bug can be generalized to “git name-rev
--stdin” does not work with --no-undefined nor --name-only
The --name-only case seems clear to me that we should fix
it. It’s misleading to return the sha instead of “undefined”
for a rev without a symbolic name, as a sha could be a symbolic
name.
I think we can also make the argument that --no-undefined should
also die in --stdin mode when given a rev without any symbolic
names.
Hmph, the manual page documents:
--stdin::
Transform stdin by substituting all the 40-character SHA-1
hexes (say $hex) with "$hex ($rev_name)". When used with
--name-only, substitute with "$rev_name", omitting $hex
altogether. Intended for the scripter's use.
It is unfortunate that the way this option works is confusingly a
bit different from what we learned to expect from the --stdin option
other subcommands like "git pack-objects --stdin" takes. In short,
these are not equivalent:
git name-rev [<options>] $string
printf "%s" "$string" | xargs git name-rev [<options>]
printf "%s" "$string" | git name-rev --stdin [<options>]
The first two are supposed to be the equivalent, but the third one
is different by design. Its `--stdin` mode is expected to read
something like this [*]:
$ cat sample.txt
A revision that exists 2ae0a9cb82 is shown here,
and its full name is 2ae0a9cb8298185a94e5998086f380a355dd8907
while its tree object is 70d105cc79e63b81cfdcb08a15297c23e60b07ad
which probably is undescribable hexdigits.
and its designed use is to annotate its input into a more reader
friendly from with refnames where possible.
No wonder! This elucidates why I found the user experience of the --stdin
mode a bit unexpected, as it would simply echo back the input when it couldn’t find a
valid object or refname rather than return an error message. I think I totally missed
the verbiage in the documentation that states its meant to **substitute** text in stdin.
Makes sense to echo back the input if nothing useful could be found.
Here is what we get:
$ git name-rev --stdin <sample.txt
A revision that exists 2ae0a9cb82 is shown here,
and its full name is 2ae0a9cb8298185a94e5998086f380a355dd8907 (master)
while its tree object is 70d105cc79e63b81cfdcb08a15297c23e60b07ad
which probably is undescribable hexdigits.
I notice a few things.
* An abbreviated commit object name is not affected;
* A 40-digit string that cannot be described with a reference is
left alone, without "undefined".
It might be debatable that the latter may want to be annotated with
"undefined", but as the command does not molest other noise strings
like "its" "full" name" in the input, I think the current behaviour
is preferred over appending "(undefined)" after a string we do not
recognize that happens to be 40-hex.
When used with --name-only, we see this:
$ git name-rev --name-only --stdin <sample.txt
A revision that exists 2ae0a9cb82 is shown here,
and its full name is master
while its tree object is 70d105cc79e63b81cfdcb08a15297c23e60b07ad
which probably is undescribable hexdigits.
So, as far as I can see, it is working as described. If there is
any bug in the things I saw and shown here, it is that it is
misleading to claim that this behaviour is intended for scripter's
use. It clearly is not scripter friendly when you want to run
"name-rev" on unbounded number of object names you have, which may
not fit on the command line, as that is not how it was designed to
be used.
Two possible things we can do to improve are
* Fix the documentation; it is not for scripters but for annotating
text with object names.
Makes sense to update the documentation to make it clear what --stdin mode is
meant to do.
* Possibly add --names-from-standard-input option that would behave
more like "we cannot afford to stuff all object names on the
command line, so we feed them one by one from the standard input"
mode the "--stdin" option of other subcommands use.
I do not think the latter is so important, as it is perfectly OK to
use xargs to split the large input into multiple invocations of
name-rev. This is unlike "pack-objects --stdin" where the command
needs to see _all_ input in a single invocation.
[Footnote]
* The sample input was produced with
$ cat >sample.txt <<EOF
A revision that exists $(git rev-parse --short HEAD) is shown here,
and its full name is $(git rev-parse HEAD)
while its tree object is $(git rev-parse HEAD:)
which probably is undescribable hexdigits.
EOF
if you want to try it at home ;-)
Thanks you for the example..
On 24/12/2021 19:42, Junio C Hamano wrote:
* The sample input was produced with
$ cat >sample.txt <<EOF
A revision that exists $(git rev-parse --short HEAD) is shown here,
and its full name is $(git rev-parse HEAD)
while its tree object is $(git rev-parse HEAD:)
which probably is undescribable hexdigits.
EOF
if you want to try it at home ;-)
The ` $(git rev-parse HEAD:) ` technique is serendipitous.
I'd forgotten that was how to get the commit object's tree for further
investigation, as I'd need it for my `deadhead` query [1], as used
regularly in the Git-for-Windows merging-rebase (see also [2]).
Philip
[1]
https://lore.kernel.org/git/be7ec330-2b2c-a01f-c7ca-e5e752493ee0@iee.email/
[2]
https://lore.kernel.org/git/nycvar.QRO.7.76.6.2112101528200.90@tvgsbejvaqbjf.bet/