bug#70526: 29.2; package-vc-upgrade failed with error message "File is not under version control"

["Yi Yue" via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

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Hi all:


I encountered the following Backtrace information when invoking
`package-vc-upgrade'.


Debugger entered--Lisp error: (error "File is not under version control")
  error("File is not under version control")
  vc-deduce-fileset-1(t nil nil)
  vc-deduce-fileset(t)
  vc-pull()
  ......


After some edebug debugging and reading the source code, I found that
this error occurs if the buffer where `package-vc-upgrade' is called is
not under a git repository. Additionally, if the current buffer of the
command invocation does not correspond to a specific file, then the
command can execute normally.


After reading the implementation of `package-vc-upgrade', I found that it
binds `default-directory' to the package's path. However, the internally
called `vc-pull' function, which uses `vc-deduce-fileset-1', first
utilizes `buffer-file-name' instead of `default-directory' to fetch
version control backend related information, which leads to this error.


In my past usage, I did not encounter this error, probably because I
usually invoked it within a file buffer under a git repository, or used
the command in a buffer provided by `list-packages'. Here is one
solution I used:


(when (eq emacs-major-version 29)
  (defun yy/package-vc-upgrade-advice (upfun pkg-desc)
    (with-temp-buffer
      (funcall upfun pkg-desc)))
  (advice-add 'package-vc-upgrade :around 'yy/package-vc-upgrade-advice))


In a minimal environment with emacs -Q, the following steps can
reproduce my issue:


;; a simple package by purcell
(package-vc-install "https://github.com/purcell/unfill")
;; then try to upgrade it in a buffer that buffer-file-name is not nil
;; and the file is not under Git version control system.
M-x package-vc-upgrade unfill RET
;; now the error may occurs


Regards


YI YUE

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