Diffing and merging

Author: ben

book/11-git-internals/sections/environment.asc

@@ -105,16 +105,26 @@ The default is a value like `git/2.0.0`.
 
 ==== Diffing and Merging
 
-*GIT_DIFF_OPTS*
+*GIT_DIFF_OPTS* is a bit of a misnomer.
+The only valid values are `-u<n>` or `--unified=<n>`, which controls the number of context lines shown in a `git diff` command.
 
-*GIT_EXTERNAL_DIFF*
+*GIT_EXTERNAL_DIFF* is used as an override for the `diff.external` configuration value.
+If it's set, Git will invoke this program when `git diff` is invoked.
 
-*GIT_DIFF_PATH_COUNTER*
+*GIT_DIFF_PATH_COUNTER* and *GIT_DIFF_PATH_TOTAL* are useful when you're using `GIT_EXTERNAL_DIFF` or `diff.external`.
+The former represents which file in a series is being diffed (starting with 1), and the latter is the total number of files in the batch.
 
-*GIT_DIFF_PATH_TOTAL*
+*GIT_MERGE_VERBOSITY* controls the output for the recursive merge strategy.
+The allowed values are as follows:
 
-*GIT_MERGE_VERBOSITY*
+* 0 outputs nothing, except possibly a single error message.
+* 1 shows only conflicts.
+* 2 also shows file changes.
+* 3 shows when files are skipped because they haven't changed.
+* 4 shows all paths as they are processed.
+* 5 and above show detailed debugging information.
 
+The default value is 2.
 
 ==== Debugging