`mob start` can silently discard local commits if branch has unpushed changes

[pfichtner]

Summary (TL;DR)

If a developer forgets to run mob start before making changes, then runs mob next, Mob creates a local commit.
If they then run mob start to catch up with the latest mob session, Mob force-resets the branch to origin/mob/main and silently discards the local commit.
The work is only recoverable via git reflog.

This is different from a push rejection: the problem is mob start always doing a hard reset.

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Environment

• Mob version: 5.4.2

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Scenario (Step-by-step)

Dev A (correct flow)

1. mob start
2. make changes
3. mob next # pushes successfully

Remote mob/main moves forward.

Dev B (forgot to run mob start)

1. Already on the mob/main branch
2. Starts working without mob start.
3. Makes changes locally.
4. Runs mob next:

• Local commit exists on mob/main.
• Push get rejected b/c remote advanced — but the commit is still in the local branch.

4. Dev B runs mob start to "catch up":

• Force-reset happens.
• The local commit from mob next is deleted from the branch and working tree.
• Only recoverable via git reflog.

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Why this is problematic

• The push rejection is not the root cause; it’s just a common trigger.
• The real problem: mob start always resets the branch, regardless of local commits.
• This makes the workflow fragile, and it’s easy for developers to lose work silently.

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Expected behavior

mob start should detect local commits not on the remote and refuse to reset blindly.

Example:

“You have local commits on mob/main not on origin/mob/main. Please pull/rebase/push your changes before running mob start.”

Alternatively, provide an option to rebase local commits instead of overwriting them.

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Suggested improvements

1) Safety check before reset

git log origin/mob/main..mob/main

If non-empty → abort mob start with clear instructions.

2) Guidance after failed mob next

When the push fails:

“Your commit exists locally but is not pushed. Run git pull --rebase origin mob/main and then mob next. Do not run mob start before resolving divergence.”

3) Optional rejoin-local mode

mob start --rejoin-local

Automatically rebase local commits onto origin/mob/main instead of discarding them.

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Why this matters

Mob abstracts Git for collaboration. In this case, that abstraction hides a destructive Git operation, leading to silent data loss.
A simple safety check would prevent this from happening in real-world sessions.