added changelog for useragent change

Entire-Checkpoint: 4ef80d38ebda

Author: Soph

CHANGELOG.md

@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/).
 ### Changed
 
 - HTTP auth now matches git's own flow: try anonymous first and only consult the credential helper after a 401, instead of proactively running `git credential fill` for every endpoint. This stops git-sync from dropping into an interactive `Username:`/`Password:` prompt on unauthenticated hosts and from leaking tokens to public repos. Expired credentials (401, or 403 from token services like Cloudflare) trigger a helper `reject` so the next run starts clean; the helper runs with `GIT_TERMINAL_PROMPT=0` to fail fast rather than block on a tty ([#65](https://github.com/entireio/git-sync/pull/65))
+- Outbound requests now identify git-sync in the User-Agent instead of advertising only go-git's default. Git wire-protocol traffic (smart-HTTP info-refs, upload-pack/receive-pack, and the protocol v2 `agent=` capability) sends `git-sync/<version> go-git/<v>` to preserve go-git attribution; non-git HTTP (the GitHub repo metadata call during bootstrap) sends just `git-sync/<version>`. A new `internal/useragent` package centralises the format, wired from `versioninfo.Version` at startup so `--version` and the User-Agent agree, and overridable by SDK consumers ([#69](https://github.com/entireio/git-sync/pull/69))
 - Bootstrap planning streams the commit-graph fetch instead of materializing the full commit set: a new `ExtractCommitParents` path parses the `tree:0` pack incrementally, extracting only `(commit -> parent hashes)` tuples with a bounded LRU for delta resolution. On `torvalds/linux` this cut peak Go heap from 5.42 GiB to 1.47 GiB (-73%), peak RSS from 5.69 GiB to 1.63 GiB (-71%), and wall time from 32m to 19m (-40%) ([#61](https://github.com/entireio/git-sync/pull/61))
 
 ### Fixed