Hello Lars,
for your questions:
> If there are multiple branches with the same hash then your script would pick
> the first one. Can you imagine a situation where this would be a problem?
I can't think of a good solution to resolve it automatically. Maybe a script
could print that there are multiple possibilities and it choose the first
branch in the list.
> Plus, you are looking only at local branches. Wouldn't it make sense to look
> at remote branches, too?
This is also related to restoring tags. If we go this way, we should have this
priority list:
- local branches
- remote branches
- tags
> Submodule processing is already quite slow if you have many of them. I wonder
> how much this approach would affect the performance.
Yes. It takes a few seconds to iterate all the submodules. It could be improved
if the processing wouldn't be based on slow Bash scripts spawning lot's of
sub-shells to execute multiple Git commands.
Is there a way to avoid detached DEADs at the beginning?
Many submodules are attached to a reference and get detached to a hash of the
same reference. It would be better, if they never get detached when the current
and new hash are the same.
Kind regards
Patrick
________________________________________
Von: git-ow...@vger.kernel.org [git-ow...@vger.kernel.org]" im Auftrag von
"Lars Schneider [larsxschnei...@gmail.com]
Gesendet: Montag, 19. Juni 2017 11:30
Bis: Patrick Lehmann
Cc: Git Mailinglist; Stefan Beller
Betreff: Re: Restoring detached HEADs after Git operations
> On 19 Jun 2017, at 10:46, Patrick Lehmann <patrick.lehm...@plc2.de> wrote:
>
> Hello,
>
> I wrote a Bash script to recover branch names after Git operations have
> create detached HEADs in a Git repository containing lots of Git submodules.
> The script works recursively.
I did run into this situation myself and therefore
I understand your motivation. I've CC'ed Stefan as
he is a Submodule expert!
> I would like to see:
> a) that script or algorithm being integrated into Git by default
> b) that as a default behavior for all Git operations creating detached HEADs
>
> That's the command:
> --------------------------------
> git submodule foreach --recursive 'HEAD=$(git branch --list | head -n 1); if
> [[ "$HEAD" == *HEAD* ]]; then REF=$(git rev-parse HEAD); FOUND=0; for Branch
> in $(git branch --list | grep "^ " | sed -e "s/ //" ); do if [[ "$(git
> rev-parse "$Branch")" == $REF ]]; then echo -e " \e[36mCheckout
> $Branch...\e[0m"; git checkout $Branch; FOUND=1; break; fi done; if [[ $FOUND
> -eq 0 ]]; then echo -e " \e[31mNo matching branch found.\e[0m"; fi else echo
> -e " \e[36mNothing to do.\e[0m"; fi'
> --------------------------------
>
> How does it work:
> 1. It uses git submodule foreach to dive into each Git submodule and execute
> a series of Bash commands.
> 2. It's reading the list of branches and checks if the submodule is in
> detached mode. The first line contains the string HEAD.
> 3. Retrieve the hash of the detached HEAD
> 4. Iterate all local branches and get their hashes
> 5. Compare the branch hashes with the detached HEAD's hash. If it matches do
> a checkout.
If there are multiple branches with the same hash then
your script would pick the first one. Can you imagine a
situation where this would be a problem?
Plus, you are looking only at local branches. Wouldn't it
make sense to look at remote branches, too?
> 6. Report if no branch name was found or if a HEAD was not in detached mode.
>
> The Bash code with line breaks and indentation:
> --------------------------------
> HEAD=$(git branch --list | head -n 1)
> if [[ "$HEAD" == *HEAD* ]]; then
> REF=$(git rev-parse HEAD)
> FOUND=0
> for Branch in $(git branch --list | grep "^ " | sed -e "s/ //" ); do
There is a convenient "git for-each-ref" function to iterate over
branches in scripts. See here an example:
https://github.com/larsxschneider/scotty/blob/master/admin/oss-fork.sh#L88
> if [[ "$(git rev-parse "$Branch")" == $REF ]]; then
> echo -e " \e[36mCheckout $Branch...\e[0m"
> git checkout $Branch
> FOUND=1
> break
> fi
> done
> if [[ $FOUND -eq 0 ]]; then
> echo -e " \e[31mNo matching branch found.\e[0m"
> fi
> else
> echo -e " \e[36mNothing to do.\e[0m"
> fi
> --------------------------------
>
> Are their any chances to get it integrated into Git?
>
> I tried to register that code as a Git alias, but git config complains about
> quote problem not showing where. It neither specifies if it's a single or
> double quote problem. Any advice on how to register that piece of code as an
> alias?
Try to escape ". See here for an example:
https://github.com/Autodesk/enterprise-config-for-git/blob/master/config.include#L76-L94
> If wished, I think I could expand the script to also recover hash values to
> Git tags if no branch was found.
It would be indeed nice to see the tagged version on my prompt.
--
Submodule processing is already quite slow if you have many of them.
I wonder how much this approach would affect the performance.
- Lars
