Re: [PATCH v5 0/5] Sparse checkout: fix bug with worktree of bare repo

>
> This series is now based on v2.35.0 since that contains all of the necessary
> topics.
>
> This patch series includes a fix to the bug reported by Sean Allred [1] and
> diagnosed by Eric Sunshine [2].
>
> The root cause is that 'git sparse-checkout init' writes to the worktree
> config without checking that core.bare or core.worktree are set in the
> common config file. This series fixes this, but also puts in place some
> helpers to prevent this from happening in the future.
>
> ATTENTION: I have significantly redesigned the series since previous
> versions, so most of this cover letter is new.
>
>  * Patch 1 updates documentation around extensions.worktreeConfig in a few
>    places to improve discoverability. Several cross links are added to make
>    it easy to find the related areas. (The documentation for the changes to
>    'git sparse-checkout' are delayed to patch 4.)
>
>  * Patch 2 introduces the init_worktree_config() helper which follows the
>    documented instructions to enable extensions.worktreeConfig as well as
>    move the core.bare and core.worktree config values. This update does not
>    modify core.repositoryFormatVersion, since this is not needed
>    specifically for extensions.worktreeConfig.
>
>  * Patch 3 adds a new repo_config_set_worktree_gently() helper method so we
>    can internally adjust a config value within a worktree, at least if
>    extensions.worktreeConfig is enabled. (It will write to the common config
>    file if the extension is not enabled.)
>
>  * Patch 4 modifies the sparse-checkout builtin to use
>    init_worktree_config() and repo_config_set_worktree_gently() in ways that
>    fix the reported bug. The behavior change here is that it will no longer
>    upgrade the repository format version, since that is not needed for
>    extensions.worktreeConfig.
>
>  * Patch 5 updates 'git worktree add' to copy the worktree config from the
>    current worktree to the new one (while unsetting core.bare=true and
>    core.worktree=*) along with copying the sparse-checkout patterns file.
>
> [1]
> https://lore.kernel.org/git/CABceR4bZmtC4rCwgxZ1BBYZP69VOUca1f_moJoP989vTUZWu9Q@mail.gmail.com/
> [2]
> https://lore.kernel.org/git/CAPig+cQ6U_yFw-X2OWrizB1rbCvc4bNxuSzKFzmoLNnm0GH8Eg@mail.gmail.com/
>
>
> Updates in v5
> =============
>
>  * Cleaned up documentation as per Elijah's suggestions.
>  * Removed unnecessary conflicting change in git-sparse-checkout.txt
>  * Fixed an ambiguous comment about moving config values.

> Updates in v4
> =============
>
>  * Rebased to v2.35.0
>  * Fixed memory leak (was leaking repo_git_path() result)
>  * Added additional documentation updates so curious users can discover the
>    intricacies of extensions.worktreeConfig from multiple entry points.
>  * Significantly reduced the amount of changes to config.c.
>  * 'git sparse-checkout' no longer upgrades the repository format.
>  * Dropped the update to upgrade_repository_format(), since it is not
>    needed.
>  * Dropped the 'git worktree init-worktree-config' subcommand in favor of a
>    helper method called by 'git sparse-checkout'
>  * Many others because of the significant changes required by the above
>    items.
>
> Thanks, -Stolee
>
> Derrick Stolee (5):
>   Documentation: add extensions.worktreeConfig details
>   worktree: create init_worktree_config()
>   config: add repo_config_set_worktree_gently()
>   sparse-checkout: set worktree-config correctly
>   worktree: copy sparse-checkout patterns and config on add
>
>  Documentation/config/extensions.txt   | 31 ++++++++++++
>  Documentation/git-config.txt          |  8 ++-
>  Documentation/git-sparse-checkout.txt | 16 ++++--
>  Documentation/git-worktree.txt        | 11 +++--
>  builtin/sparse-checkout.c             | 28 +++++------
>  builtin/worktree.c                    | 60 +++++++++++++++++++++++
>  config.c                              | 35 ++++++++++++--
>  config.h                              |  8 +++
>  sparse-index.c                        | 10 ++--
>  t/t1091-sparse-checkout-builtin.sh    | 35 ++++++++++----
>  t/t2400-worktree-add.sh               | 46 +++++++++++++++++-
>  worktree.c                            | 70 +++++++++++++++++++++++++++
>  worktree.h                            | 21 ++++++++
>  13 files changed, 333 insertions(+), 46 deletions(-)
>
>
> base-commit: 89bece5c8c96f0b962cfc89e63f82d603fd60bed
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1101%2Fderrickstolee%2Fsparse-checkout%2Fbare-worktree-bug-v5
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1101/derrickstolee/sparse-checkout/bare-worktree-bug-v5
> Pull-Request: https://github.com/gitgitgadget/git/pull/1101
>
> Range-diff vs v4:
>
>  1:  459e09dedd7 ! 1:  1bd5f26271c Documentation: add extensions.worktreeConfig details
>      @@ Commit message
>           within git-sparse-checkout.txt, but a behavior change is needed before
>           making those updates.
>
>      +    Helped-by: Elijah Newren <newren@gmail.com>
>           Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
>
>        ## Documentation/config/extensions.txt ##
>      @@ Documentation/git-config.txt: from all available files.
>       - present. If not it's the same as `--local`.
>       + enabled. If not it's the same as `--local`. Note that `$GIT_DIR`
>       + is equal to `$GIT_COMMON_DIR` for the main worktree, but is of the
>      -+ form `.git/worktrees/<worktree-name>/` for other worktrees. See
>      ++ form `$GIT_DIR/worktrees/<worktree-name>/` for other worktrees. See
>       + linkgit:git-worktree[1] to learn how to enable
>       + `extensions.worktreeConfig`.
>
>      @@ Documentation/git-worktree.txt: CONFIGURATION FILE
>       -already present in the config file, they will be applied to the main
>       -working trees only.
>       +present in the common config file and `extensions.worktreeConfig` is
>      -+disabled, then they will be applied to the main working trees only.
>      ++disabled, then they will be applied to the main working tree only.
>
>        In order to have configuration specific to working trees, you can turn
>        on the `worktreeConfig` extension, e.g.:
>      @@ Documentation/git-worktree.txt: them to the `config.worktree` of the main workin
>       - - `core.worktree` and `core.bare` should never be shared
>       + - `core.worktree` should never be shared.
>       +
>      -+ - `core.bare` should not be shared unless the value is `core.bare=false`.
>      ++ - `core.bare` should not be shared if the value is `core.bare=true`.
>
>         - `core.sparseCheckout` is recommended per working tree, unless you
>           are sure you always use sparse checkout for all working trees.
>  2:  d262a76b448 ! 2:  2a2c350112e worktree: create init_worktree_config()
>      @@ worktree.h: void strbuf_worktree_ref(const struct worktree *wt,
>       + *
>       + * 1. Add extensions.worktreeConfig=true in the common config file.
>       + *
>      -+ * 2. If the common config file has a core.worktree value or core.bare is
>      -+ *    set to true, then those values are moved to the main worktree's
>      -+ *    config.worktree file.
>      ++ * 2. If the common config file has a core.worktree value, then that value
>      ++ *    is moved to the main worktree's config.worktree file.
>      ++ *
>      ++ * 3. If the common config file has a core.bare enabled, then that value
>      ++ *    is moved to the main worktree's config.worktree file.
>       + *
>       + * If extensions.worktreeConfig is already true, then this method
>       + * terminates early without any of the above steps. The existing config
>  3:  110d5e0546c = 3:  802b28a9510 config: add repo_config_set_worktree_gently()
>  4:  fbfaa17797c ! 4:  08b89d17ccf sparse-checkout: set worktree-config correctly
>      @@ Documentation/git-sparse-checkout.txt: COMMANDS
>       - (extensions.worktreeConfig, core.sparseCheckout,
>       - core.sparseCheckoutCone) if they are not already enabled, and
>       - write a set of patterns to the sparse-checkout file from the
>      -- list of arguments following the 'set' subcommand. Update the
>      -- working directory to match the new patterns.
>       + Enable the necessary sparse-checkout config settings
>      -+ (`core.sparseCheckout` and possibly `core.sparseCheckoutCone`) if
>      -+ they are not already enabled, and write a set of patterns to the
>      -+ sparse-checkout file from the list of arguments following the
>      -+ 'set' subcommand. Update the working directory to match the new
>      -+ patterns.
>      -++
>      ++ (`core.sparseCheckout`, `core.sparseCheckoutCone`, and
>      ++ `index.sparse`) if they are not already set to the desired values,
>      ++ and write a set of patterns to the sparse-checkout file from the
>      +  list of arguments following the 'set' subcommand. Update the
>      +  working directory to match the new patterns.
>      + +
>       +To ensure that adjusting the sparse-checkout settings within a worktree
>       +does not alter the sparse-checkout settings in other worktrees, the 'set'
>       +subcommand will upgrade your repository config to use worktree-specific
>      @@ Documentation/git-sparse-checkout.txt: COMMANDS
>       +the 'set' subcommand are stored in the worktree-specific sparse-checkout
>       +file. See linkgit:git-worktree[1] and the documentation of
>       +`extensions.worktreeConfig` in linkgit:git-config[1] for more details.
>      - +
>      +++
>        When the `--stdin` option is provided, the patterns are read from
>        standard in as a newline-delimited list instead of from the arguments.
>      -@@ Documentation/git-sparse-checkout.txt: interact with your repository until it is disabled.
>      -  By default, these patterns are read from the command-line arguments,
>      -  but they can be read from stdin using the `--stdin` option. When
>      -  `core.sparseCheckoutCone` is enabled, the given patterns are interpreted
>      -- as directory names as in the 'set' subcommand.
>      -+ as directory names as in the 'set' subcommand. The sparsity defined
>      -+ by the arguments to the 'add' subcommand are added to the patterns
>      -+ in the worktree-specific sparse-checkout file.
>      -
>      - 'reapply'::
>      -  Reapply the sparsity pattern rules to paths in the working tree.
>      + +
>
>        ## builtin/sparse-checkout.c ##
>       @@
>  5:  bb9e550ff3d ! 5:  85779dfaed3 worktree: copy sparse-checkout patterns and config on add
>      @@ t/t1091-sparse-checkout-builtin.sh: test_expect_success 'add to sparse-checkout'
>       + cat repo/.git/info/sparse-checkout >old &&
>       + test_when_finished cp old repo/.git/info/sparse-checkout &&
>       + test_when_finished git -C repo worktree remove ../worktree &&
>      -+ git -C repo sparse-checkout set "/*" &&
>      ++ git -C repo sparse-checkout set --no-cone "/*" &&
>       + git -C repo worktree add --quiet ../worktree 2>err &&
>       + test_must_be_empty err &&
>       + new=repo/.git/worktrees/worktree/info/sparse-checkout &&
>
> --
> gitgitgadget