OneDrive Git Commit Skill

Problem

Git repositories stored in OneDrive folders often fail with fatal: mmap failed: Invalid argument when executing porcelain commands like git commit, git status, or git push.

This occurs because OneDrive's file system layer interferes with git's memory-mapped file operations.

Solution

Use git plumbing commands to bypass the mmap issue and create commits manually.

When to Use This Skill

Invoke this skill when:

• User requests git commit in a repo under OneDrive path (/c/Users/*/OneDrive/)
• Git command returns fatal: mmap failed: Invalid argument
• Standard git commit fails repeatedly

Step-by-Step Commit Process

1. Configure Git Memory Settings

Reduce memory usage to minimize mmap calls:

cd "$REPO_PATH"
git config core.packedGitWindowSize 1m
git config core.packedGitLimit 1m
git config pack.windowMemory 1m
git config pack.packSizeLimit 1m

2. Create Git Objects for Modified Files

For each file to commit, create a blob object:

git hash-object -w path/to/file1
git hash-object -w path/to/file2
# Save the SHA hashes returned

3. Update Git Index

Register each file in the index with its SHA:

git update-index --add --cacheinfo 100644,<SHA>,path/to/file1
git update-index --add --cacheinfo 100644,<SHA>,path/to/file2

Mode codes:

• 100644 = regular file
• 100755 = executable file
• 120000 = symbolic link

4. Create Tree Object

Generate tree from current index:

TREE_SHA=$(git write-tree)
echo $TREE_SHA

5. Get Parent Commit

Retrieve current HEAD SHA:

PARENT_SHA=$(git rev-parse HEAD)
echo $PARENT_SHA

6. Create Commit Object

Build commit with message and metadata:

COMMIT_MESSAGE="feat: Your commit message here

Detailed description if needed

Co-Authored-By: Claude <noreply@anthropic.com>"

COMMIT_SHA=$(echo "$COMMIT_MESSAGE" | git commit-tree $TREE_SHA -p $PARENT_SHA)
echo $COMMIT_SHA

7. Update Branch Reference

Move HEAD to new commit:

git update-ref refs/heads/master $COMMIT_SHA

Replace master with current branch name if different.

8. Verify Commit

Check commit was created:

git log -1 --oneline

Push to Remote

If remote is configured:

git remote -v
git push origin master

Note: Push may also fail with mmap error. If so, user must push via Git GUI or GitHub Desktop.

Alternative: Git GUI

If plumbing commands fail, recommend:

• Git GUI (installed with Git for Windows)
• GitHub Desktop
• GitKraken

These tools don't use mmap and work reliably on OneDrive.

Common Errors

"fatal: not a valid object name"

• Check SHA hashes are correct
• Ensure files were successfully written with hash-object

"fatal: refs/heads/master: not a valid SHA1"

• Use git rev-parse HEAD to get valid parent commit
• If repo is new, omit -p $PARENT_SHA from commit-tree

"error: unable to write sha1 file"

• OneDrive is syncing - wait for sync to complete
• Temporarily pause OneDrive sync during git operations

Notes

• This workflow bypasses all git porcelain commands
• Works when standard git fails on OneDrive
• Commits are identical to normal git commits
• No data corruption or integrity issues
• Recommended only when necessary (mmap errors)

Example Complete Workflow

cd "$REPO_PATH"

# Configure memory
git config core.packedGitWindowSize 1m

# Create objects
SHA1=$(git hash-object -w file1.txt)
SHA2=$(git hash-object -w file2.txt)

# Update index
git update-index --add --cacheinfo 100644,$SHA1,file1.txt
git update-index --add --cacheinfo 100644,$SHA2,file2.txt

# Create tree
TREE=$(git write-tree)

# Get parent
PARENT=$(git rev-parse HEAD)

# Create commit
COMMIT=$(echo "feat: Update files" | git commit-tree $TREE -p $PARENT)

# Update branch
git update-ref refs/heads/master $COMMIT

# Verify
git log -1 --oneline

Success Criteria

Commit is successful when:

• git log -1 shows new commit
• Commit SHA is different from parent
• Files are included in commit tree
• No mmap errors occur

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Last Updated: November 2025 Tested On: Windows 11, Git 2.43+, OneDrive sync enabled