Revert "Use HEAD instead of hardcoded branch"

This reverts commit 6651fd88.

Reason for revert: broke some cros builds (check original CL for
discussion)

Original change's description:
> Use HEAD instead of hardcoded branch
>
> Repositories may have different default branches. This ensures to fetch
> remote HEAD branch which is default branch. Only downside to this
> approach is that actual branch (e.g. origin/main) reference won't be
> updated. Since we don't need it for this particular case, it should be
> fine to use HEAD.
>
> R=​apolito@google.com, ehmaldonaldo@chromium.org
>
> Bug: 1155492
> Recipe-Nontrivial-Roll: chromiumos
> Recipe-Nontrivial-Roll: infra
> Recipe-Nontrivial-Roll: build_limited_scripts_slave
> Change-Id: Ib2e6e50901a0a10ed647acea3aeb517b83567702
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2580190
> Reviewed-by: Anthony Polito <apolito@google.com>
> Commit-Queue: Josip Sokcevic <sokcevic@google.com>

TBR=ehmaldonado@chromium.org,apolito@google.com,infra-scoped@luci-project-accounts.iam.gserviceaccount.com,sokcevic@google.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1155492
Recipe-Nontrivial-Roll: chromiumos
Recipe-Nontrivial-Roll: infra
Recipe-Nontrivial-Roll: build_limited_scripts_slave
Recipe-Nontrivial-Roll: build
Change-Id: Ibd9f67bea71ee4a644b1077a365dbcd2a2c469f0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2597065Reviewed-by: Anthony Polito <apolito@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
Auto-Submit: Josip Sokcevic <sokcevic@google.com>

recipes/README.recipes.md

@@ -534,7 +534,7 @@ upload.
 Args:
   * branch (str): new branch name, which must not yet exist.
   * name (str): step name.
-  * upstream (str): to origin/main.
+  * upstream (str): to origin/master.
   * kwargs: Forwarded to '__call__'.
 
 — **def [rebase](/recipes/recipe_modules/git/api.py#328)(self, name_prefix, branch, dir_path, remote_name=None, \*\*kwargs):**

recipes/recipe_modules/git/api.py

@@ -211,16 +211,16 @@ class GitApi(recipe_api.RecipeApi):
 
       # There are five kinds of refs we can be handed:
       # 0) None. In this case, we default to api.buildbucket.gitiles_commit.ref.
-      # 1) A fully qualified branch name, e.g. 'refs/heads/main'.
+      # 1) A fully qualified branch name, e.g. 'refs/heads/master'.
       #    Chop off 'refs/heads/' and now it matches case (4).
       # 2) A 40-character SHA1 hash.
       # 3) A fully-qualifed arbitrary ref, e.g. 'refs/foo/bar/baz'.
-      # 4) A branch name, e.g. 'main'.
+      # 4) A branch name, e.g. 'master'.
       # Note that 'FETCH_HEAD' can be many things (and therefore not a valid
       # checkout target) if many refs are fetched, but we only explicitly fetch
       # one ref here, so this is safe.
       if not ref:                                  # Case 0.
-        ref = self.m.buildbucket.gitiles_commit.ref or 'HEAD'
+        ref = self.m.buildbucket.gitiles_commit.ref or 'master'
 
       # If it's a fully-qualified branch name, trim the 'refs/heads/' prefix.
       if ref.startswith('refs/heads/'):            # Case 1.
@@ -396,7 +396,7 @@ class GitApi(recipe_api.RecipeApi):
     Args:
       * branch (str): new branch name, which must not yet exist.
       * name (str): step name.
-      * upstream (str): to origin/main.
+      * upstream (str): to origin/master.
       * kwargs: Forwarded to '__call__'.
     """
     env = self.m.context.env

recipes/recipe_modules/git/examples/full.expected/basic.json

@@ -16,7 +16,7 @@
       "git",
       "fetch",
       "origin",
-      "HEAD",
+      "master",
       "--recurse-submodules",
       "--progress"
     ],

recipes/recipe_modules/git/examples/full.expected/basic_file_name.json

@@ -16,7 +16,7 @@
       "git",
       "fetch",
       "origin",
-      "HEAD",
+      "master",
       "--recurse-submodules",
       "--progress"
     ],

recipes/recipe_modules/git/examples/full.expected/basic_submodule_update_force.json

@@ -16,7 +16,7 @@
       "git",
       "fetch",
       "origin",
-      "HEAD",
+      "master",
       "--recurse-submodules",
       "--progress"
     ],

recipes/recipe_modules/git/examples/full.expected/basic_tags.json

@@ -16,7 +16,7 @@
       "git",
       "fetch",
       "origin",
-      "HEAD",
+      "master",
       "--recurse-submodules",
       "--progress",
       "--tags"

recipes/recipe_modules/git/examples/full.expected/can_fail_build.json

@@ -16,7 +16,7 @@
       "git",
       "fetch",
       "origin",
-      "HEAD",
+      "master",
       "--recurse-submodules",
       "--progress"
     ],

recipes/recipe_modules/git/examples/full.expected/cannot_fail_build.json

@@ -16,7 +16,7 @@
       "git",
       "fetch",
       "origin",
-      "HEAD",
+      "master",
       "--recurse-submodules",
       "--progress"
     ],

recipes/recipe_modules/git/examples/full.expected/count-objects_delta.json

@@ -37,7 +37,7 @@
       "git",
       "fetch",
       "origin",
-      "HEAD",
+      "master",
       "--recurse-submodules",
       "--progress"
     ],

recipes/recipe_modules/git/examples/full.expected/count-objects_failed.json

@@ -16,7 +16,7 @@
       "git",
       "fetch",
       "origin",
-      "HEAD",
+      "master",
       "--recurse-submodules",
       "--progress"
     ],

recipes/recipe_modules/git/examples/full.expected/count-objects_with_bad_output.json

@@ -16,7 +16,7 @@
       "git",
       "fetch",
       "origin",
-      "HEAD",
+      "master",
       "--recurse-submodules",
       "--progress"
     ],

recipes/recipe_modules/git/examples/full.expected/count-objects_with_bad_output_fails_build.json

@@ -16,7 +16,7 @@
       "git",
       "fetch",
       "origin",
-      "HEAD",
+      "master",
       "--recurse-submodules",
       "--progress"
     ],

recipes/recipe_modules/git/examples/full.expected/git-cache-checkout.json

@@ -64,7 +64,7 @@
       "git",
       "fetch",
       "origin",
-      "HEAD",
+      "master",
       "--recurse-submodules",
       "--progress"
     ],

recipes/recipe_modules/git/examples/full.expected/platform_win.json

@@ -16,7 +16,7 @@
       "git",
       "fetch",
       "origin",
-      "HEAD",
+      "master",
       "--recurse-submodules",
       "--progress"
     ],

recipes/recipe_modules/git/examples/full.expected/rebase_failed.json

@@ -16,7 +16,7 @@
       "git",
       "fetch",
       "origin",
-      "HEAD",
+      "master",
       "--recurse-submodules",
       "--progress"
     ],

recipes/recipe_modules/git/examples/full.expected/remote_not_origin.json

@@ -18,7 +18,7 @@
       "git",
       "fetch",
       "not_origin",
-      "HEAD",
+      "master",
       "--recurse-submodules",
       "--progress"
     ],

recipes/recipe_modules/git/examples/full.expected/set_got_revision.json

@@ -16,7 +16,7 @@
       "git",
       "fetch",
       "origin",
-      "HEAD",
+      "master",
       "--recurse-submodules",
       "--progress"
     ],