hermes - 💡(How to fix) Fix hermes version shows '860 commits behind' after checking out latest tag v2026.5.29.2 [2 pull requests]

Bug Description

After updating to the latest stable release via git tag checkout, hermes version incorrectly reports "Update available: 860 commits behind — run 'hermes update'", even though the user is on the latest tagged release.

Steps to Reproduce

1. Start on an older version (e.g., v0.15.1 / v2026.5.29)
2. Run hermes update — it reports "Already up to date!" (incorrect, since newer tag exists)
3. Manually checkout the latest tag: cd ~/.hermes/hermes-agent && git checkout v2026.5.29.2
4. Run hermes version
5. Output shows:
   • Correct version: Hermes Agent v0.15.2 (2026.5.29.2)
   • Incorrect update warning: Update available: 860 commits behind — run 'hermes update'

Root Cause Analysis

The version check logic appears to compare the current HEAD against origin/main using git log HEAD..origin/main. When the user checks out a tag (detached HEAD), this comparison is invalid because:

• The latest tag (v2026.5.29.2) is only 3 commits ahead of the previous tag
• But origin/main has diverged significantly (860 commits) from the tagged release
• The user is not actually "behind" — they are on the latest stable release, just not on the main branch

Expected Behavior

1. hermes update should detect when a newer tag exists and update to it, not just check if the current branch is up to date with origin.
2. hermes version should either:
   • Compare against the latest tag instead of origin/main, OR
   • Detect detached HEAD state and suppress the "commits behind" warning, OR
   • Clarify that the user is on a tagged release and the behind count refers to main branch divergence

Environment

• Hermes Agent: v0.15.1 -> v0.15.2
• Git origin: https://github.com/NousResearch/hermes-agent.git
• OS: macOS 26.5

Suggested Fix

Modify the version/update check logic to:

1. Check for latest tags when determining if an update is available
2. Handle detached HEAD state gracefully in version reporting
3. Distinguish between "behind latest tag" and "behind main branch"

This issue was encountered when trying to update from v0.15.1 to v0.15.2. The hermes update command reported "Already up to date!" but the newer tag existed and had to be manually checked out.