shell-integration: fix ssh-env SetEnv clobbering user SSH config

[j0hnm4r5]

Problem

Ghostty's ssh-env shell integration uses -o "SetEnv COLORTERM=truecolor" when wrapping SSH commands. OpenSSH treats command-line -o SetEnv options as replacements for all SetEnv entries in ~/.ssh/config, not additions. This silently drops any user-configured SetEnv variables.

For example, a user with this in their SSH config:

Host myserver
  SetEnv MY_VAR=hello

...would find MY_VAR empty after SSHing through Ghostty with ssh-env enabled.

Reference: #10871

Fix

Replace -o "SetEnv COLORTERM=truecolor" with the additive pattern: set COLORTERM=truecolor locally before the SSH call and forward it via SendEnv.

SendEnv is additive — it does not clobber SetEnv entries in ~/.ssh/config.

Trade-off: SendEnv requires AcceptEnv COLORTERM on the remote server (unlike SetEnv). But this was already the case for TERM_PROGRAM/TERM_PROGRAM_VERSION, so it's a consistent and acceptable approach.

Changes

All 5 shell integration files updated with the same pattern:

• SetEnv COLORTERM=truecolor option removed
• COLORTERM added to the existing SendEnv option
• COLORTERM=truecolor set as a local env var on the execute line (so SendEnv has something to forward)

Test plan

• Enable ssh-env in Ghostty config: shell-integration-features = ssh-env
• Add SetEnv MY_VAR=hello under a host in ~/.ssh/config and AcceptEnv MY_VAR in /etc/ssh/sshd_config on the remote
• SSH to that host — echo $MY_VAR should return hello (was empty before this fix)
• echo $COLORTERM returns truecolor (requires AcceptEnv COLORTERM)
• echo $TERM_PROGRAM still propagates (same AcceptEnv requirement as before)

[ghostty-vouch]

Hi @j0hnm4r5, thanks for your interest in contributing!

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This PR will be closed automatically. See https://github.com/ghostty-org/ghostty/blob/main/CONTRIBUTING.md for more details.

[jparise]

!vouch

[jparise]

This make sense to me and is a good overall improvement. Thanks!

[jparise]

@j0hnm4r5 was there more you wanted to iterate on before marking this as "Ready for review"?

[j0hnm4r5]

Sorry, I wasn't expecting this to get seen/vouched so quickly! I just double checked the code and a few SSH connections and I think we're good; I'll mark it as ready.