Bug: `git show` honors path filters only for the first commit

git version: 2.36.0
OS: macOS Monterey 12.2.1
Installed via: homebrew

Bug summary: When `git show` is invoked with more than one commit, it only respects the `<path>` filters for the first commit.

This is best illustrated with an example. In git's own source repo, invoke `git show --oneline --name-only ecc7c8841d 961b130d20 d3115660b4` and observe the files these commits touch (the `--oneline --name-only` arguments are to make this example short; they're not relevant to the bug):

    $ git show --oneline --numstat ecc7c8841d 961b130d20 d3115660b4
    ecc7c8841d repo_read_index: add config to expect files outside
sparse patterns
    2       0       Documentation/config.txt
    27      0       Documentation/config/sparse.txt
    1       0       cache.h
    14      0       config.c
    1       0       environment.c
    2       1       sparse-index.c
    19      0       t/t1090-sparse-checkout-scope.sh
    961b130d20 branch: add --recurse-submodules option for branch creation
    3       0       Documentation/config/advice.txt
    26      11      Documentation/config/submodule.txt
    18      1       Documentation/git-branch.txt
    1       0       advice.c
    1       0       advice.h
    141     0       branch.c
    29      0       branch.h
    38      6       builtin/branch.c
    38      0       builtin/submodule--helper.c
    61      0       submodule-config.c
    34      0       submodule-config.h
    9       2       submodule.c
    3       0       submodule.h
    292     0       t/t3207-branch-submodule.sh
    d3115660b4 branch: add flags and config to inherit tracking
    2       1       Documentation/config/branch.txt
    17      7       Documentation/git-branch.txt
    1       1       Documentation/git-checkout.txt
    1       1       Documentation/git-switch.txt
    42      7       branch.c
    2       1       branch.h
    4       2       builtin/branch.c
    4       2       builtin/checkout.c
    3       0       config.c
    16      0       parse-options-cb.c
    2       0       parse-options.h
    10      1       t/t2017-checkout-orphan.sh
    23      0       t/t2027-checkout-track.sh
    28      0       t/t2060-switch.sh
    33      0       t/t3200-branch.sh
    17      0       t/t7201-co.sh

Now invoke the same command but filtered on files under the `Documentation/` directory. Observe that this path is only respected for the first commit:

    $ git show --oneline --numstat ecc7c8841d 961b130d20 d3115660b4 --
Documentation
    ecc7c8841d repo_read_index: add config to expect files outside
sparse patterns
    2       0       Documentation/config.txt
    27      0       Documentation/config/sparse.txt
    961b130d20 branch: add --recurse-submodules option for branch creation
    3       0       Documentation/config/advice.txt
    26      11      Documentation/config/submodule.txt
    18      1       Documentation/git-branch.txt
    1       0       advice.c
    1       0       advice.h
    141     0       branch.c
    29      0       branch.h
    38      6       builtin/branch.c
    38      0       builtin/submodule--helper.c
    61      0       submodule-config.c
    34      0       submodule-config.h
    9       2       submodule.c
    3       0       submodule.h
    292     0       t/t3207-branch-submodule.sh
    d3115660b4 branch: add flags and config to inherit tracking
    2       1       Documentation/config/branch.txt
    17      7       Documentation/git-branch.txt
    1       1       Documentation/git-checkout.txt
    1       1       Documentation/git-switch.txt
    42      7       branch.c
    2       1       branch.h
    4       2       builtin/branch.c
    4       2       builtin/checkout.c
    3       0       config.c
    16      0       parse-options-cb.c
    2       0       parse-options.h
    10      1       t/t2017-checkout-orphan.sh
    23      0       t/t2027-checkout-track.sh
    28      0       t/t2060-switch.sh
    33      0       t/t3200-branch.sh
    17      0       t/t7201-co.sh

The expected output should be:

    $ git show --oneline --numstat ecc7c8841d 961b130d20 d3115660b4 --
Documentation
    ecc7c8841d repo_read_index: add config to expect files outside
sparse patterns
    2       0       Documentation/config.txt
    27      0       Documentation/config/sparse.txt
    961b130d20 branch: add --recurse-submodules option for branch creation
    3       0       Documentation/config/advice.txt
    26      11      Documentation/config/submodule.txt
    18      1       Documentation/git-branch.txt
    d3115660b4 branch: add flags and config to inherit tracking
    2       1       Documentation/config/branch.txt
    17      7       Documentation/git-branch.txt
    1       1       Documentation/git-checkout.txt
    1       1       Documentation/git-switch.txt

Bonus: Surprisingly, the `<path>` *is* respected for commits that
don't have any files satisfying the `<path>`. For example, the
following command correctly excludes commit `f36d4f8316` from the
output because it doesn't contain any files under `Documentation/`:

    $ git show --oneline --numstat ecc7c8841d f36d4f8316 961b130d20
d3115660b4 -- Documentation
    ecc7c8841d repo_read_index: add config to expect files outside
sparse patterns
    2       0       Documentation/config.txt
    27      0       Documentation/config/sparse.txt
    961b130d20 branch: add --recurse-submodules option for branch creation
    3       0       Documentation/config/advice.txt
    26      11      Documentation/config/submodule.txt
    18      1       Documentation/git-branch.txt
    1       0       advice.c
    1       0       advice.h
    141     0       branch.c
    29      0       branch.h
    38      6       builtin/branch.c
    38      0       builtin/submodule--helper.c
    61      0       submodule-config.c
    34      0       submodule-config.h
    9       2       submodule.c
    3       0       submodule.h
    292     0       t/t3207-branch-submodule.sh
    d3115660b4 branch: add flags and config to inherit tracking
    2       1       Documentation/config/branch.txt
    17      7       Documentation/git-branch.txt
    1       1       Documentation/git-checkout.txt
    1       1       Documentation/git-switch.txt
    42      7       branch.c
    2       1       branch.h
    4       2       builtin/branch.c
    4       2       builtin/checkout.c
    3       0       config.c
    16      0       parse-options-cb.c
    2       0       parse-options.h
    10      1       t/t2017-checkout-orphan.sh
    23      0       t/t2027-checkout-track.sh
    28      0       t/t2060-switch.sh
    33      0       t/t3200-branch.sh
    17      0       t/t7201-co.sh

Cheers,

Dan Li

--

Daniel Li dan@danielyli.com