git/builtin/difftool.c

/*
 * "git difftool" builtin command
 *
 * This is a wrapper around the GIT_EXTERNAL_DIFF-compatible
 * git-difftool--helper script.
 *
 * This script exports GIT_EXTERNAL_DIFF and GIT_PAGER for use by git.
 * The GIT_DIFF* variables are exported for use by git-difftool--helper.
 *
 * Any arguments that are unknown to this script are forwarded to 'git diff'.
 *
 * Copyright (C) 2016 Johannes Schindelin
 */
#define USE_THE_REPOSITORY_VARIABLE
#include "builtin.h"

#include "abspath.h"
#include "config.h"
#include "copy.h"
#include "run-command.h"
#include "environment.h"
#include "gettext.h"
#include "hex.h"
#include "parse-options.h"
#include "read-cache-ll.h"
#include "repository.h"
#include "sparse-index.h"
#include "strvec.h"
#include "strbuf.h"
#include "lockfile.h"
#include "object-file.h"
#include "object-store-ll.h"
#include "dir.h"
#include "entry.h"
#include "setup.h"

static int trust_exit_code;

static const char *const builtin_difftool_usage[] = …;

static int difftool_config(const char *var, const char *value,
			   const struct config_context *ctx, void *cb)
{ … }

static int print_tool_help(void)
{ … }

static int parse_index_info(char *p, int *mode1, int *mode2,
			    struct object_id *oid1, struct object_id *oid2,
			    char *status)
{ … }

/*
 * Remove any trailing slash from $workdir
 * before starting to avoid double slashes in symlink targets.
 */
static void add_path(struct strbuf *buf, size_t base_len, const char *path)
{ … }

/*
 * Determine whether we can simply reuse the file in the worktree.
 */
static int use_wt_file(const char *workdir, const char *name,
		       struct object_id *oid)
{ … }

struct working_tree_entry { … };

static int working_tree_entry_cmp(const void *cmp_data UNUSED,
				  const struct hashmap_entry *eptr,
				  const struct hashmap_entry *entry_or_key,
				  const void *keydata UNUSED)
{ … }

/*
 * The `left` and `right` entries hold paths for the symlinks hashmap,
 * and a SHA-1 surrounded by brief text for submodules.
 */
struct pair_entry { … };

static int pair_cmp(const void *cmp_data UNUSED,
		    const struct hashmap_entry *eptr,
		    const struct hashmap_entry *entry_or_key,
		    const void *keydata UNUSED)
{ … }

static void add_left_or_right(struct hashmap *map, const char *path,
			      const char *content, int is_right)
{ … }

struct path_entry { … };

static int path_entry_cmp(const void *cmp_data UNUSED,
			  const struct hashmap_entry *eptr,
			  const struct hashmap_entry *entry_or_key,
			  const void *key)
{ … }

static void changed_files(struct hashmap *result, const char *index_path,
			  const char *workdir)
{ … }

static int ensure_leading_directories(char *path)
{ … }

/*
 * Unconditional writing of a plain regular file is what
 * "git difftool --dir-diff" wants to do for symlinks.  We are preparing two
 * temporary directories to be fed to a Git-unaware tool that knows how to
 * show a diff of two directories (e.g. "diff -r A B").
 *
 * Because the tool is Git-unaware, if a symbolic link appears in either of
 * these temporary directories, it will try to dereference and show the
 * difference of the target of the symbolic link, which is not what we want,
 * as the goal of the dir-diff mode is to produce an output that is logically
 * equivalent to what "git diff" produces.
 *
 * Most importantly, we want to get textual comparison of the result of the
 * readlink(2).  get_symlink() provides that---it returns the contents of
 * the symlink that gets written to a regular file to force the external tool
 * to compare the readlink(2) result as text, even on a filesystem that is
 * capable of doing a symbolic link.
 */
static char *get_symlink(const struct object_id *oid, const char *path)
{ … }

static int checkout_path(unsigned mode, struct object_id *oid,
			 const char *path, const struct checkout *state)
{ … }

static void write_file_in_directory(struct strbuf *dir, size_t dir_len,
			const char *path, const char *content)
{ … }

/* Write the file contents for the left and right sides of the difftool
 * dir-diff representation for submodules and symlinks. Symlinks and submodules
 * are written as regular text files so that external diff tools can diff them
 * as text files, resulting in behavior that is analogous to to what "git diff"
 * displays for symlink and submodule diffs.
 */
static void write_standin_files(struct pair_entry *entry,
			struct strbuf *ldir, size_t ldir_len,
			struct strbuf *rdir, size_t rdir_len)
{ … }

static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
			struct child_process *child)
{ … }

static int run_file_diff(int prompt, const char *prefix,
			 struct child_process *child)
{ … }

int cmd_difftool(int argc,
		 const char **argv,
		 const char *prefix,
		 struct repository *repo UNUSED)
{ … }