Currently, h5i does not provide functionality for editing the message of previously-made commits. As projects develop, and as different aspects of past commits grow more relevant to current development, this immutability may be an inconvenience.

To address this issue, the edit-message function provides functionality for editing the message of a previously-made commit. The function may be called as follows:

h5i edit-message <oid> --edit <new message>

The function returns the new OID of the commit whose message was edited.

Commits with or without dependencies may be edited. If the commit whose message was edited has dependencies, the parent OID of each dependency is updated accordingly.

Example usage:

$ h5i log
commit 8ae70031018fc596eacede251391cf69130feac4
Author:    Srivarun Kankanala <[email protected]>

    test commit 2, dependent on test commit 1

────────────────────────────────────────────────────────────
commit b945b7bc3f1c6c409b193f3122a437755dfe7d06
Author:    Srivarun Kankanala <[email protected]>

    test commit 1

────────────────────────────────────────────────────────────

$ h5i edit-message b945b7bc3f1c6c409b193f3122a437755dfe7d06 --edit "new message"
 Editing commit message for b945b7bc
 New commit OID: f2afb521550377ef1c8928e5338d46877866d25c

$ h5i log
commit 0c4f991ce3c7be437aabfdfc90ff1c343006cf04
Author:    Srivarun Kankanala <[email protected]>

    test commit 2, dependent on test commit 1

────────────────────────────────────────────────────────────
commit f2afb521550377ef1c8928e5338d46877866d25c
Author:    Srivarun Kankanala <[email protected]>

    new message

────────────────────────────────────────────────────────────

$ h5i edit-message 0c4f991ce3c7be437aabfdfc90ff1c343006cf04 --edit "test commit 2, dependent on new message commit"
 Editing commit message for 0c4f991c
 New commit OID: 209ab5640f7e7439ae6730eafedfa505b96da784

$ h5i log
commit 209ab5640f7e7439ae6730eafedfa505b96da784
Author:    Srivarun Kankanala <[email protected]>

    test commit 2, dependent on new message commit

────────────────────────────────────────────────────────────
commit f2afb521550377ef1c8928e5338d46877866d25c
Author:    Srivarun Kankanala <[email protected]>

    new message

────────────────────────────────────────────────────────────

Attached are screenshots of the h5i UI after each of the calls to edit-message in the example above.

Intial:

First Call:

Second Call:

Comprehensive testcases are included in CI.

UPDATE:
Instead of using filter-branch, which poses several stability concerns, this new implementation of edit-message employs a Breadth-First Search to find the target commit from the HEAD commit. The process for editing the message of a commit is as follows:

• Each commit stores caused_by and causes fields in its h5i Note, maintaining bidirectional causal links.
• A BFS from HEAD through Git parent links locates the target commit, recording the path from target to HEAD as an ordered sequence.
• The target commit is rewritten with the new message, producing a new OID. Its h5i Note is moved to the new OID.
• The path from target to HEAD is iterated linearly. Each commit is rewritten with remapped parent OIDs, and its h5i Note is moved to the new OID.
• A second linear pass over the rewritten commits updates any stale OID references in their caused_by and causes Note fields.
• Commits outside the rewritten path whose caused_by referenced an old OID have their Notes patched in place, without OID changes.
• HEAD is advanced to the new tip commit.