Re: `git fetch --refmap=<refspec>… <repository> <refspec>… ` providing NON-empty <refspec> to the --refmap ALSO causes Git to ignore the configured refspecs

The problem with the doc is "how to override". From https://git-scm.com/docs/git-fetch#Documentation/git-fetch.txt---refmapltrefspecgt it seems we need to `git fetch --refmap='' --refmap=<refspec>` to really override configuration variables. I guess the inner working is like this: first for-loop traverses configuration variable `remote.<remote>.fetch` collecting <refspec>s into a list, then second for-loop traverses `--refmap=<refspec>`s, clears the list when an empty string is encountered, appends to the list when a non-empty string is encountered. Maybe I'm just daydreaming...

I think the correct use case of empty string, is to specify more --refmap=<refspec>s after it (like in https://git-scm.com/docs/git-config#Documentation/git-config.txt-pushpushOption ), otherwise the mapping (to operate upon foo,bar and baz) would be empty.

Sorry that I didn't use examples to express my intended use scenarios clearly!

After I searched "empty value" or "empty string" in https://git-scm.com/docs/git-config yesterday, the most intuitive behavior of `git fetch --refmap` (for me) was: `git fetch <remote> <branch>...` uses `remote.<remote>.fetch`; `git fetch --refmap=<refspec> --refmap=<refspec> <remote> <branch>...` uses `remote.<remote>.fetch` and all the `--refmap=<refspec>`s; `git fetch --refmap='' --refmap=<refspec> --refmap=<refspec> <remote> <branch>...` uses all the `--refmap=<refspec>`s;

Here is an example of all of these being used at the same time.
1. Normally, user uses `fetch-safe` which uses `git fetch
--refmap=<refspec>` to use whatever mappings specified by
`remote.<remote>.fetch` and also let our backup logic sneak in.
2. Occasionally, upstream is rebased and our backup logic (refspec
without `+`) blocks the process because of `--atomic`.
2.1. When that happens, user uses `fetch-bak-current-time` which uses
`git fetch --refmap='' --refmap=<refspec>` to clear whatever mappings
specified by `remote.<remote>.fetch` and use our another backup logic
(refspec with `+`).
2.2. After old tips are saved, user uses `git fetch --force` to use
whatever mappings specified by `remote.<remote>.fetch`;

Currently [1.] is not working because --refmap=<not empty string!> clears `remote.<remote>.fetch` instead of merging with it. Hence this bug report.

cd '/'; cd '/'; rm --force --recursive -- './test_git2'; mkdir "$_"; cd "$_"; mkdir --parents -- './server' './client';

git -C './server' init --bare './repo.git' git --git-dir='./server/repo.git' --work-tree='.' commit --allow-empty -m "$((++number))" git --git-dir='./server/repo.git' --work-tree='.' commit --allow-empty -m "$((++number))" git -C './server/repo.git' branch branch1; git -C './server/repo.git' branch branch2

git -C './client' init './repo' git -C './client/repo' config set --local 'alias.fetch-safe' '!git_fetch_safe(){ server="$1"; shift; git fetch --atomic --refmap='\''refs/*:refs/namespaces/'\''"$server"'\''_backup/refs/*'\'' "$server" "$@"; };git_fetch_safe' git -C './client/repo' config set --local 'alias.fetch-bak-current-time' '!git_fetch_bak_current_time(){ server="$1"; shift; git -c '\''remote.'\''"$server"'\''_backup.url=.'\'' --namespace="$server"'\''_backup'\'' fetch --refmap='\''refs/*:refs/namespaces/'\''"$server"'\''_backup_'\''"$(date +'%Y%m%d%H%M%S')"'\''/refs/*'\'' "$server"'_backup' "$@"; git fetch --atomic --refmap='\'\'' --refmap='\''+refs/*:refs/namespaces/'\''"$server"'\''_backup/refs/*'\'' "$server" "$@"; };git_fetch_bak_current_time' git -C './client/repo' remote add server 'file://'"$(realpath './server/repo.git')" git -C './client/repo' remote --verbose git -C './client/repo' config list --local --show-scope --show-origin git -C './client/repo' fetch-safe server branch1 branch2 git -C './client/repo' show-ref git -C './client/repo' lg --all --decorate-refs='*'

git --git-dir='./server/repo.git' --work-tree='.' commit --allow-empty -m "$((++number))" git -C './server/repo.git' branch --force branch1; git -C './server/repo.git' branch --force branch2 git -C './client/repo' fetch-safe server branch1 branch2 git -C './client/repo' show-ref git -C './client/repo' lg --all --decorate-refs='*'

git --git-dir='./server/repo.git' --work-tree='.' commit --allow-empty -m "$((++number))" --amend git -C './server/repo.git' branch --force branch1; git -C './server/repo.git' branch --force branch2 git -C './client/repo' fetch-safe server branch1 branch2 git -C './client/repo' show-ref git -C './client/repo' lg --all --decorate-refs='*' git -C './client/repo' fetch-bak-current-time server branch1 branch2 git -C './client/repo' show-ref git -C './client/repo' lg --all --decorate-refs='*' git -C './client/repo' fetch --force server branch1 branch2 git -C './client/repo' show-ref git -C './client/repo' lg --all --decorate-refs='*'

On Thu, Sep 5, 2024 at 4:47 AM Junio C Hamano <gitster@pobox.com> wrote: