Re: [PATCH v2] gitk: Add support of SHA256 repo

> This patch adds a basic support of SHA256 Git repository to Gitk, so
> that Gitk can show and operate on both SHA1 and SHA256 repos
> gracefully.  Since SHA256 has a longer ID length (64 char) than SHA1
> (40 char), many field widths are adjusted to fit with it.
> 
> A caveat is that the configuration of auto selection length is shared
> between SHA1 and SHA256 repos.  That is, once when this value is saved
> and read, it's applied to both repo types, which may result in shorter
> selection than the full SHA256 ID.  We may introduce another
> individual config for sha256 (actually I did write in the first
> version), but for simplicity, the common config is used as of writing
> this.
> 
> Many lines still refer "sha1" although they may point to both SHA1 and
> SHA256.  They are left untouched for making the changes simpler.
> 
> This patch is based on the early work by Rostislav Krasny:
>   https://patchwork.kernel.org/project/git/patch/pull.979.git.1623687519832.gitgitgadget@gmail.com
> I refreshed, revised and extended to the latest state.
> 
> Signed-off-by: Takashi Iwai <tiwai@suse.de>
> ---
> 
> v1: https://lore.kernel.org/20250320154136.23262-1-tiwai@suse.de
> v1->v2:
> - Fix other procs using fixed 40 length
> - Don't use tabs
> - Drop autosellensha256 config
> - Some code simplification
> - Fix patch description

> @@ -12491,6 +12513,17 @@ if {$tclencoding == {}} {
>      puts stderr "Warning: encoding $gitencoding is not supported by Tcl/Tk"
>  }
>  
> +# Use object format as hash algorightm (either "sha1" or "sha256")
> +set hashalgorithm [exec git rev-parse --show-object-format]
> +if {$hashalgorithm eq "sha1"} {
> +    set hashlength 40
> +} elseif {$hashalgorithm eq "sha256"} {
> +    set hashlength 64
> +} else {
> +    puts stderr "Unknown hash algorithm: $hashalgorithm"
> +    exit 1
> +}
> +
>  set gui_encoding [encoding system]
>  catch {
>      set enc [exec git config --get gui.encoding]