Experimental Builtin Rebase fails to use the committer identity signing key

[nebularg]

• I was not able to find an open or closed issue matching what I'm seeing

Setup

• Which version of Git for Windows are you using? Is it 32-bit or 64-bit?

$ git --version --build-options

git version 2.19.0.windows.1
cpu: x86_64
built from commit: d96bb8bc6c636a8869140e860e72e7bdf64bd790
sizeof-long: 4
sizeof-size_t: 8

• Which version of Windows are you running? Vista, 7, 8, 10? Is it 32-bit or 64-bit?

$ cmd.exe /c ver

Microsoft Windows [Version 10.0.17134.285]

• What options did you set as part of the installation? Or did you choose the
  defaults?

Editor Option: VIM
Path Option: Cmd
Plink Path: C:\Program Files\TortoiseGit\bin\TortoiseGitPlink.exe
SSH Option: Plink
CURL Option: OpenSSL
CRLF Option: CRLFAlways
Bash Terminal Option: MinTTY
Performance Tweaks FSCache: Enabled
Use Credential Manager: Enabled
Enable Symlinks: Enabled
Enable Builtin Rebase: Enabled
Enable Builtin Stash: Enabled

Details

• Which terminal/shell are you running Git from? e.g Bash/CMD/PowerShell/other

mintty/Bash

• What commands did you run to trigger this issue? If you can provide a
  Minimal, Complete, and Verifiable example
  this will help us understand the issue.

$ git config user.signingkey
DC35E715

$ git config commit.gpgsign
true

$ git rebase -i
error: switch `S' requires a value

• What did you expect to occur after running these commands?

The keyid should be optional and default to user.signingkey and rebase should run.

• What actually happened instead?

Rebase errors about an optional value. It works correctly if you pass -SDC35E715, set rebase.useBuiltin to false, or set commit.gpgsign to false.

[shiftkey]

#1847 also has some extra information about the issue

[dscho]

Thank you all for the excellent analysis! I figured out the problem: by mistake, the optional argument of the -S option was not optional but mandatory. Technically, only the rebase -i fix is required to fix this here issue, but I was already working on the built-in stuff, and the non-interactive rebase also needs this fix.