git-commit-graph:tldr:00a37

This command involves two Git commands: git rev-parse and git commit-graph write.

1. git rev-parse is a command that is used to transform various values into a unique commit object identifier, also known as a SHA-1 hash. In the given command, git rev-parse is used to get the commit hash for the HEAD reference.

   ${HEAD} is a placeholder representing the commit reference to be resolved. The exact value of HEAD can vary depending on the state of the repository. For example, it could be a branch name like master or a specific commit hash.

   The command git rev-parse ${HEAD} will output the commit hash associated with the HEAD reference.

2. The output of git rev-parse is then piped (|) as input to the next command git commit-graph write.

   git commit-graph write is a command that generates or updates commit-graph files in Git repositories. Commit-graph files improve performance for operations that involve commit traversal, like git log or git blame, by creating a more efficient data structure.

   In the given command, git commit-graph write is used with the following options:

   • --stdin-commits: This option instructs Git to read commit hashes from the standard input (the output of git rev-parse ${HEAD}) instead of directly specifying them.
   • --append: This option tells Git to append the commit graph data to the existing commit-graph file, if any, rather than overwriting it completely.

   Combining these options with the piped commit hash from git rev-parse, git commit-graph write --stdin-commits --append takes the commit hash associated with HEAD and updates the commit-graph file with the new commit data, preserving any previous data if present.