[PATCH 0/3] http: add support for HTTP 429 rate limit retries

This patch series adds support for handling HTTP 429 (Too Many Requests)
responses in Git's HTTP client with automatic retry logic.

Git hosting services can implement rate limiting to protect their
infrastructure. When these limits are reached, servers respond with HTTP 429
status codes, potentially including a Retry-After header to indicate when
the client should retry. Currently, Git treats these responses as fatal
errors, forcing users to manually retry their operations.

This series implements automatic retry support with three new configuration
options:

 * http.maxRetries: Controls the maximum number of retry attempts (default:
   0, opt-in behavior)

 * http.retryAfter: Provides a fallback delay when the server doesn't
   include a Retry-After header (default: -1, fail if no header)

 * http.maxRetryTime: Sets an upper limit on any single retry delay
   (default: 300 seconds) to prevent indefinite blocking

The implementation includes:

Patch 1: Core HTTP 429 retry logic with support for RFC-compliant
Retry-After headers (both delay-seconds and HTTP-date formats),
comprehensive configuration options, and fail-fast behavior for excessive
delays. Includes extensive test coverage.

Patch 2: Fixes a pre-existing memory leak in show_http_message() that became
more visible with the new retry logic.

Patch 3: Adds trace2 instrumentation to enable monitoring and debugging of
retry operations in production environments.

The retry behavior is disabled by default (maxRetries = 0), requiring
explicit opt-in, ensuring backward compatibility while providing a robust
solution for environments that need rate limit handling.

There was a previous attempt to add retry support [1], which was not merged.
It had support for 50x status codes. Should they be supported here too?

[1] https://lore.kernel.org/git/20201012184806.166251-3-smcallis@google.com/ (local)

Vaidas Pilkauskas (3): http: add support for HTTP 429 rate limit retries
remote-curl: fix memory leak in show_http_message() http: add trace2 logging
for retry operations

Documentation/config/http.adoc | 24 ++ http-push.c | 8 + http-walker.c | 5 +
http.c | 171 ++++++++++++- http.h | 2 + remote-curl.c | 18 +- t/meson.build
| 1 + t/t5584-http-429-retry.sh | 429 +++++++++++++++++++++++++++++++++ 8
files changed, 650 insertions(+), 8 deletions(-) create mode 100755
t/t5584-http-429-retry.sh

-- 2.50.1

Vaidas Pilkauskas (3):
  http: add support for HTTP 429 rate limit retries
  remote-curl: fix memory leak in show_http_message()
  http: add trace2 logging for retry operations

 Documentation/config/http.adoc |  24 ++
 http-push.c                    |   8 +
 http-walker.c                  |   5 +
 http.c                         | 171 ++++++++++++-
 http.h                         |   2 +
 remote-curl.c                  |  18 +-
 t/meson.build                  |   1 +
 t/t5584-http-429-retry.sh      | 429 +++++++++++++++++++++++++++++++++
 8 files changed, 650 insertions(+), 8 deletions(-)
 create mode 100755 t/t5584-http-429-retry.sh


base-commit: 6ab38b7e9cc7adafc304f3204616a4debd49c6e9
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-2008%2Fvaidas-shopify%2Fretry-after-v1
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-2008/vaidas-shopify/retry-after-v1
Pull-Request: https://github.com/gitgitgadget/git/pull/2008
-- 
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