config: borrow refcounted referencescmn/config-borrow-entry

This changes the get_entry() method to return a refcounted version of
the config entry, which you have to free when you're done.

This allows us to avoid freeing the memory in which the entry is stored
on a refresh, which may happen at any time for a live config.

For this reason, get_string() has been forbidden on live configs and a
new function get_string_buf() has been added, which stores the string in
a git_buf which the user then owns.

The functions which parse the string value takea advantage of the
borrowing to parse safely and then release the entry.

1 files changed, 12 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index b88488e61..6f9e1f1cb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -25,6 +25,11 @@ v0.22 + 1
   set and query which identity will be used when writing to the
   reflog.
 
+* `git_config_entry_free()` frees a config entry.
+
+* `git_config_get_string_buf()` provides a way to safely retrieve a
+  string from a non-snapshot configuration.
+
 ### API removals
 
 ### Breaking API changes
@@ -53,6 +58,13 @@ v0.22 + 1
       `git_repository_detach_head()`
     * `git_reset()`
 
+* `git_config_get_entry()` now gives back a ref-counted
+  `git_config_entry`. You must free it when you no longer need it.
+
+* `git_config_get_string()` will return an error if used on a
+  non-snapshot configuration, as there can be no guarantee that the
+  returned pointer is valid.
+
 v0.22
 ------